Terminal device, base station device, communication method, and integrated circuit

ABSTRACT

Provided is technology relating to: a terminal device, a base station device, a communication method, and an integrated circuit capable of efficiently performing a Radio Resource Control procedure. The terminal device is configured to, when receiving, from the base station device, an RRC message including information on a target cell, random access information relating to a coverage level, and a timer relating to a handover and indicating the handover, start the timer relating to the handover and execute a random access to the target cell using the random access information relating to the coverage level of the target cell.

TECHNICAL FIELD

The present invention relates to technology of a terminal device, a basestation device, a communication method, and an integrated circuit thatefficiently perform a Radio Resource Control procedure.

BACKGROUND ART

The 3rd Generation Partnership Project (3GPP), which is astandardization project, has standardized Evolved Universal TerrestrialRadio Access (EUTRA), in which high-speed communication is realized byadopting an Orthogonal Frequency-Division Multiplexing (OFDM)communication method and flexible scheduling in a unit of prescribedfrequency and time called a resource block. EUTRA may also be referredto as Long Term Evolution (LTE).

Moreover, the 3GPP has been considering LTE Advanced (also referred toas LTE-A) which realizes higher-speed data transfer and has uppercompatibility with LTE.

For LTE Advanced, a cost reduction (also referred to as low complexity)of a terminal device used for Machine Type Communication (MTC) orMachine To Machine Communication (M2M) has been considered (NPL 1).Hereinafter, a terminal device or a communication device designed forMTC/M2M and having the function capable of (supporting) a cost reductionand/or Coverage Enhancement is also referred to as Machine TypeCommunication User Equipment (MTCUE). However, the use of such aterminal device is not limited to Machine Type Communication nor MachineTo Machine Communication.

The 3GPP has proposed, in order to realize low cost MTCUE, the narrowingof a transmission and reception bandwidth, a reduction of the number ofantenna ports/the number of RF chains, a reduction of the transmissionand reception data transfer rate, adoption of a Half-duplex FrequencyDivision Duplex scheme, a reduction of transmit and receive power, anextension of Discontinuous Reception intervals, and the like.Furthermore, the 3GPP has also proposed, as a method of realizing thelow cost MTCUE, a reduction of the maximum bandwidth of a transmissionand reception RF circuit and a transmission and reception basebandcircuit of MTCUE, and the like.

Furthermore, in order to compensate for degradation in reception andtransmission performance due to the influence of the reduction in thenumber of the antenna ports or the like, a method has been considered inwhich downlink data or a downlink signal is repetitively transmitted toMTCUE for one data transmission, and MTCUE repetitively transmits uplinkdata or an uplink signal to a base station device for one datatransmission.

Additionally, not only cost reduction, but also Coverage Enhancement(Coverage Improvement), coverage being a transmission and receptionrange of MTCUE, has been considered. For example, with respect to spacessuch as basements which are outside the communication area due to alarge signal attenuation in the related art, the Coverage Enhancementhas been considered. In order to enhance the coverage, a method has beenconsidered in which the base station device repetitively transmitsdownlink data or a downlink signal to MTCUE, and MTCUE repetitivelytransmits uplink data or an uplink signal to the base station device(NPL 2).

For example, the base station device repetitively transmits a PhysicalBroadcast Channel PBCH to MTCUE multiple times within 40 ms.Furthermore, in a random access procedure, MTCUE repetitively transmitsthe same random access preamble with multiple resources of a PhysicalRandom Access Channel PRACH. The base station device which has receivedthe random access preamble repetitively transmits a random accessresponse message. Note that, the base station device notifies MTCUE in acell of the number of repetitions (the number of attempts) with systeminformation, or dedicatedly notifies MTCUE (NPL 2).

CITATION LIST Non Patent Literature

-   NPL 1: 3GPP TR (Technical Report) 36.888, V12.0.0 (2013-06), Study    on provision of low-cost Machine-Type Communications (MTC) User    Equipments (UEs) based on LTE (release 12)-   NPL 2: “Rel-12 agreements for MTC”, R1-143784, 3GPP TSG-RAN WG1    Meeting #78bis Ljubljana, Slovenia, 6-10 Oct. 2014

SUMMARY OF INVENTION Technical Problem

Repetitive transmissions or repetitive receptions in order to enhancecoverage may increase the time necessary for the procedure of changingfrom an idle state to a connected state. Likewise, the time necessaryfor the procedure of changing a serving cell due to a handover or thelike may also increase.

In the related art, in order to configure the maximum time for theseprocedures, a base station device notifies a terminal device of timerinformation indicating the maximum time for each of the procedures.However, these pieces of timer information of the related art have nottaken into consideration the fact that time necessary up to thecompletion of each of the procedures increases depending on the numberof repetitions of the transmission and the reception, which prevents aterminal device capable of Coverage Enhancement from using the timerinformation of the related art as it is.

For example, when the timer information of the related art is used as itis, the timer expires before a Radio Resource Control (RRC) procedure iscompleted, which in turn cause a problem that the number of failures ofthe Radio Resource Control procedure increases, and thus unnecessaryinterference signals increase. Furthermore, repetitive failures of theRadio Resource Control procedure cause another problem that powerconsumption of the terminal device increases. However, a specificsolution for these problems has not yet been considered.

In light of the above-described circumstances, an object of the presentinvention is to provide technology relating to a terminal device, a basestation device, a communication system, a communication method, and anintegrated circuit capable of efficiently performing a Radio ResourceControl procedure to solve at least one of the above-described problems.

Solution to Problem

In order to accomplish the object described above, the following meansare provided. That is, a terminal device according to an embodiment ofthe present invention is a terminal device communicating with a basestation device. The terminal device is configured to, when receiving,from the base station device, an RRC message including information on atarget cell, random access information relating to a coverage level, anda timer relating to a handover and indicating the handover, start thetimer relating to the handover, and execute a random access to thetarget cell using the random access information relating to the coveragelevel of the target cell.

Furthermore, the terminal device according to the embodiment of thepresent invention is configured to stop the timer relating to thehandover when a problem occurs in the random access to the target cell.

Furthermore, the terminal device according to the embodiment of thepresent invention is configured to support, as a value of the timerrelating to the handover, a first timer value corresponding to a cell ofa coverage level requiring a repetition, and a second timer valuecorresponding to a cell of a coverage level not requiring a repetition.

Furthermore, a base station device according to an embodiment of thepresent invention is a base station device communicating with a terminaldevice. The base station device is configured to, when causing theterminal device to execute a handover procedure using random accessinformation relating to a coverage level of a target cell, transmit, tothe terminal device, an RRC message including information on the targetcell, the random access information relating to the coverage level, anda timer relating to a handover and indicating the handover. The timerrelating to the handover is started by the terminal device, and a randomaccess to the target cell is executed by the terminal device using therandom access information relating to the coverage level of the targetcell.

Furthermore, a communication method according to an embodiment of thepresent invention is a communication method of a terminal devicecommunicating with a base station device. The communication methodincludes at least the steps of: when receiving, from the base stationdevice, an RRC message including information on a target cell, randomaccess information relating to a coverage level, and a timer relating toa handover and indicating the handover, starting the timer relating tothe handover, and executing a random access to the target cell using therandom access information relating to the coverage level of the targetcell.

Furthermore, the communication method according to the embodiment of thepresent invention, further includes the step of stopping the timerrelating to the handover when a problem occurs in the random access tothe target cell.

Furthermore, in the communication method according to the embodiment ofthe present invention, the terminal device supports, as a value of thetimer relating to the handover, a first timer value corresponding to acell of a coverage level requiring a repetition and a second timer valuecorresponding to a cell of a coverage level not requiring a repetitionare supported.

Furthermore, a communication method according to an embodiment of thepresent invention is a communication method of a base station devicecommunicating with a terminal device. The communication method includesthe step of: when causing the terminal device to execute a handoverprocedure using random access information relating to a coverage levelof a target cell, transmitting, to the terminal device, an RRC messageincluding information on the target cell, the random access informationrelating to the coverage level, and a timer relating to a handover andindicating the handover. The timer relating to the handover is startedby the terminal device, and a random access to the target cell isexecuted by the terminal device using the random access informationrelating to the coverage level of the target cell.

Furthermore, an integrated circuit according to an embodiment of thepresent invention is an integrated circuit mounted on a terminal devicecommunicating with a base station device, causes the terminal device toperform at least the functions of: when receiving, from the base stationdevice, an RRC message including information on a target cell, randomaccess information relating to a coverage level, and a timer relating toa handover and indicating the handover, starting the timer relating tothe handover; and executing a random access to the target cell using therandom access information relating to the coverage level of the targetcell.

Furthermore, an integrated circuit according to an embodiment of thepresent invention is an integrated circuit mounted on a base stationdevice communicating with a terminal device, causes the base stationdevice to perform the function of: when causing the terminal device toexecute a handover procedure using random access information relating toa coverage level of a target cell, transmitting, to the terminal device,an RRC message including information on the target cell, the randomaccess information relating to the coverage level, and a timer relatingto a handover and indicating the handover, the timer relating to thehandover is started by the terminal device, a random access to thetarget cell is executed by the terminal device using the random accessinformation relating to the coverage level of the target cell.

Although this specification discloses each embodiment in terms oftechnology relating to a terminal device, a base station device, acommunication system, a communication method, and an integrated circuitcapable of efficiently performing a Radio Resource Control procedure, acommunication method applicable to each of the embodiments is notlimited to a communication method used for EUTRA (LTE, LTE-A).

For example, the technology described in this specification may be usedin various communication systems using such as code division multipleaccess (CDMA), time division multiple access (TDMA), frequency divisionmultiple access (FDMA), orthogonal FDMA (OFDMA), single carrier FDMA(SC-FDMA), other access schemes, or the like. Furthermore, in thisspecification, “system” and “network” may be used as synonyms.

Advantageous Effects of Invention

According to the present invention, the technology of a terminal device,a base station device, a communication system, a communication method,and an integrated circuit capable of efficiently performing a RadioResource Control procedure can be provided.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a diagram illustrating an example of a constitution of aterminal device according to an embodiment of the present invention.

FIG. 2 is a diagram illustrating an example of a constitution of a basestation device according to the embodiment of the present invention.

FIG. 3 is a flowchart diagram illustrating an example of a selectionprocess of a UE timer in a terminal device according to a firstembodiment of the present invention.

FIG. 4 is a flowchart diagram illustrating an example of a start processof the UE timer in the terminal device according to the first embodimentof the present invention.

FIG. 5 is a flowchart diagram illustrating another example of the startprocess of the UE timer in the terminal device according to the firstembodiment of the present invention.

FIG. 6 is a flowchart diagram illustrating an example of an abortprocess of an RRC procedure in the terminal device according to thefirst embodiment of the present invention.

FIG. 7 is a flowchart diagram illustrating an example of a start processof a UE timer in a terminal device according to a second embodiment ofthe present invention.

FIG. 8 is a diagram illustrating a protocol stack handling control datain the terminal device and the base station device.

FIG. 9 is a diagram illustrating a protocol stack handling user data inthe terminal device and the base station device.

DESCRIPTION OF EMBODIMENTS

Technology relating to each embodiment of the present invention will besimply described below.

Channel/Signal

The LTE (EUTRA) channel includes a logical channel, a transport channel,and a physical channel. “Channel” refers to a medium used fortransmission and reception of a signal, and the logical channel definesa type of data transfer service transmitted and received in a MediumAccess Control (MAC) layer. The transport channel definescharacteristics of data transmitted over a radio interface and how thedata is transmitted.

The physical channel refers to a physical medium which carries datatransferred to a physical layer by the transport channel. In the presentinvention, the “physical channel” may be used as a synonym of “signal.”In a communication system evolved from EUTRA (LTE, LTE-A), a newphysical channel may be added, the structure (constitution) or format ofthe existing physical channel may be changed, or another structure(constitution) or format of the existing physical channel may be added;however, the description of each embodiment of the present inventionwill not be affected even in such a case.

In EUTRA, scheduling of a physical channel or a physical signal ismanaged by using a radio frame. One radio frame is 10 ms in length, andone radio frame is constituted of 10 subframes. In addition, onesubframe is constituted of two slots (i.e., one subframe is 1 ms inlength, and one slot is 0.5 ms in length). Moreover, scheduling ismanaged by using a resource block as a minimum unit of scheduling towhich a physical channel is allocated. The “resource block” is definedby a certain frequency domain constituted of a set of multiplesubcarriers (e.g., 12 subcarriers) on a frequency axis and a domainconstituted of a certain transmission time slot (one slot).

Downlink in EUTRA will be described. The downlink logical channelincludes a Broadcast Control Channel BCCH, a Paging Control ChannelPCCH, a Common Control Channel CCCH, a Dedicated Control Channel DCCH,and a Dedicated Traffic Channel DTCH.

The Broadcast Control Channel BCCH is a logical channel used forbroadcasting system information. The Paging Control Channel PCCH is alogical channel used for transmitting paging information, and used whenthe network pages a terminal device, or notifies the terminal device ofupdate of the system information. The Common Control Channel CCCH is alogical channel used for transmitting control information between theterminal device and the network. The Common Control Channel CCCH is usedby a base station device in the downlink when the terminal device hasyet to transition to a state in which Radio Resource Control (RRC)connection has been established with the network (RRC connected state orRRC_CONNECTED).

The Dedicated Control Channel DCCH is a point-to-point bi-directionalchannel, and is a logical channel used for transmitting dedicatedcontrol information between the terminal device and the network. TheDedicated Control Channel DCCH can be used between the terminal devicein the RRC connected state and the base station device. The DedicatedTraffic Channel DTCH is a point-to-point bi-directional channel, is achannel dedicated to a certain terminal device, and is a logical channelused for transferring (transmitting) user information (unicast data).

The downlink transport channel includes a Broadcast Channel BCH, aPaging Channel PCH, and a Downlink Shared Channel DL-SCH.

The Broadcast Channel BCH is broadcast throughout a cell with a formatfixedly defined in advance (Transport format). The Downlink SharedChannel DL-SCI supports a Hybrid Automatic Repeat Request (HAM, dynamiclink adaptation control, dynamic or semi-static resource allocation, andDiscontinuous Reception CORK). Furthermore, the Paging Channel PCHsupports Discontinuous Reception broadcast throughout a cell.

The downlink physical channel and physical signal of EUTRA will bedescribed.

A synchronization signal is constituted of three types of PrimarySynchronization Signals (PSS) and Secondary Synchronization Signals(SSS) constituted of 31 types of codes that are interleaved in thefrequency domain. 504 patterns of cell identifiers (Physical CellIdentities (IDs); PCIs) for identifying base station devices, and frametiming for radio synchronization are indicated by the combinations ofthe PSSs and the SSSs. The terminal device identifies the physical cellID of a received synchronization signal by cell search.

A downlink reference signal is classified into multiple types dependingon their use. For example, Cell-specific reference signals(Cell-specific RSs; CRSs) are pilot signals transmitted with prescribedpower on each cell and are downlink reference signals periodicallyrepeated in the frequency domain and the time domain under a prescribedrule. The terminal device receives the Cell-specific RS and is therebyenabled to measure the reception quality on each cell. The terminaldevice can also use the Cell-specific RS as a reference signal fordemodulation of a Physical Downlink Control Channel or a PhysicalDownlink Shared Channel transmitted at the same time as theCell-specific RS.

The sequence used for the Cell-specific RS is a sequence unique to eachcell. The Cell-specific RS may be transmitted from the base stationdevice in all downlink subframes, or may be transmitted only in downlinksubframes designated by the base station device. Furthermore, theterminal device may receive the Cell-specific RS in all the downlinksubframes, or may receive only in downlink subframes designated by thebase station device.

The downlink reference signal is also used for estimation of downlinkchannel variations. The downlink reference signal used for estimation ofdownlink channel variations is referred to as “Channel State InformationReference Signals (CSI-RSs or CSI reference signals).” Furthermore, theCSI reference signal may be a signal that is not actually transmitted oris transmitted with zero-power. On the other hand, the CSI referencesignals to he actually transmitted may also be referred to as Non ZeroPower Channel State Information Reference Signals (NZP CSI-RSs).Furthermore, a downlink radio resource used for measurement of aninterference component may be referred to as a Channel StateInformation-Interference Measurement Resource (CSI-IMR) or CSI-IMResource.

A downlink reference signal individually configured for the terminaldevice is referred to as UE-specific Reference Signals (URS), aDemodulation Reference Signal (DMRS), and is referred to for a channelcompensation process for demodulating the Physical Downlink ControlChannel, an enhanced Physical Downlink Control Channel, or the PhysicalDownlink Shared Channel.

The Physical Broadcast Channel (PBCH) is transmitted for notification(configuration) of a Master Information Block (MIB) that is shared bythe terminal devices within the cell. The base station device sends anotification of (transmits) a Master Information Block message includingthe NUB on the Physical Broadcast Channel. Information notified to(configured for) the terminal device with the Master Information Blockmessage, in other words, information notified with the MIB includes adownlink frequency bandwidth, a system frame number, configurationinformation on a physical channel relating to Hybrid ARQ (PHICH), andthe like.

The base station device transmits cell common information other than theMaster information Block to the terminal device, using a Systeminformation block Type 1 (SIB1) message by which a position andperiodicity of a subframe are pre-defined and other types of systeminformation messages (for example, System information block Type 2 toType n (n is a natural number)) dynamically scheduled in a systeminformation window (SI-window) designated by the System informationblock Type 1.

Here, each of the Master Information Block message, the Systeminformation block Type 1 message, and the system information message isa layer-3 message (RRC message). Note that, in this specification,system information (broadcast information) may refer to these RRCmessages, or may refer to information (information element) notifiedwith the Master Information Block and each system information block.

The system information message is notified in a radio resource indicatedby the Physical Downlink Control Channel on the Physical Downlink SharedChannel, and carries one piece of system information (System informationblock Type 2 to Type n (SIB2 to SIBn (n is a natural number)))classified according to the use, in a corresponding system informationwindow.

As system information, a Cell Global Identifier (CGI), which indicates acell-specific identifier, a Tracking Area Identifier (TAI) for managinga standby area in paging, random access configuration (common randomaccess configuration) information, timing adjustment information, commonradio resource configuration information for each cell, Neighboring celllist information on a list of neighboring cells having the samefrequency (different frequencies, different RATs), uplink access controlinformation, and the like are notified.

The Physical Downlink Control Channel (PDCCH) occupying several OFDMsymbols (e.g., one to four OFDM symbols) from the start of each subframeis transmitted. The Enhanced Physical Downlink Control Channel (EPDCCH)is a Physical Downlink Control Channel allocated to the OFDM symbols towhich the Physical Downlink Shared Channel (PDSCH) is allocated. ThePDCCH or EPDCCH is used for notifying each terminal device of radioresource allocation information in accordance with scheduling determinedby the base station device and control information indicating anadjustment amount for an increase or decrease in transmit power, or thelike. Hereinafter, even when the Physical Downlink Control Channel(PDCCH) alone is described, both the physical channels that is, thePDCCH and the EPDCCH, are included unless otherwise noted.

The terminal device needs to monitor the Physical Downlink ControlChannel addressed to the terminal device itself, and receive thePhysical Downlink Control Channel addressed to the terminal deviceitself, before transmitting and receiving a layer-2 message (MAC-CE) anda layer-3 message (paging, system information, or the like), and therebyacquire, from the Physical Downlink Control Channel, radio resourceallocation information called uplink grant for transmission and downlinkgrant (also referred to as downlink assignment) for reception. Note thatthe Physical Downlink Control Channel can also be designed to betransmitted in the dedicated resource block region allocated to eachterminal device by the base station device, in addition to beingtransmitted using the above-described OFDM symbols.

The Physical Downlink Shared Channel (PDSCH) is also used to notify theterminal device of, in addition to downlink data, a layer-3 message suchas paging or system information. Radio resource allocation informationon the Physical Downlink Shared Channel is indicated (notified) by thePhysical Downlink Control Channel. The Physical Downlink Shared Channelis transmitted being allocated to OFDM symbols other than the OFDMsymbols used to transmit the Physical Downlink Control Channel. In otherwords, the Physical Downlink Shared Channel and the Physical DownlinkControl Channel are time division multiplexed in a single subframe.

The Broadcast Channel BCH is mapped to the Physical Broadcast ChannelPBCH. The Paging Channel PCH and the Downlink Shared Channel DL-SCH aremapped to the Physical Downlink Shared Channel PDSCH. The PhysicalDownlink Control Channel PDCCH is used only by the physical channel.

Furthermore, in the downlink, the Paging Control Channel PCCH is mappedto the Paging Channel PCH. The Broadcast Control Channel BCCH is mappedto the Broadcast Channel BCH and the Downlink Shared Channel DL-SCH. TheCommon Control Channel CCCH, the Dedicated Control Channel DCCH, and theDedicated Traffic Channel DTCH are mapped to the Downlink Shared ChannelDL-SCH.

Next, uplink in will be described. The uplink logical channel includes aCommon Control Channel CCCH, a Dedicated Control Channel DCCH, and aDedicated Traffic Channel DTCH.

The Common Control Channel CCCH is a logical channel used fortransmitting control information between the terminal device and thenetwork, and is used by the terminal device in the uplink when theterminal device has yet to transition to a state in which Radio ResourceControl (RRC) connection has been established with the network (RRCconnected state or RRC_CONNECTED), that is RRC idle state or RRC_IDLE.

The Dedicated Control Channel DCCH is a point-to-point bi-directionalchannel, and is a logical channel used for transmitting dedicatedcontrol information between the terminal device and the network. TheDedicated Control Channel DCCH can be used between the terminal devicein the RRC connected state and the base station device. The DedicatedTraffic Channel DTCH is a point-to-point bi-directional channel, is achannel dedicated to one terminal device, and is a logical channel usedfor transferring user information (unicast data).

The uplink transport channel includes an Uplink Shared Channel UL-SCIand a Random Access Channel RACH.

The Uplink Shared Channel UL-SCH supports a Hybrid Automatic RepeatRequest (HARQ), dynamic link adaptation control, dynamic or semi-staticresource allocation, and Discontinuous Transmission (DTX). On the RandomAccess Channel RACH, limited control information is transmitted.

The uplink physical channel and physical signal of EUTRA will bedescribed.

A Physical Uplink Control Channel (PUCCH) is used for an acknowledgment(acknowledgment/negative acknowledgment; ACK/NACK) in response toreception of downlink data transmitted on the Physical Downlink SharedChannel, downlink channel (channel state) information (CSI), or anuplink radio resource allocation request (radio resource request orscheduling request (SR)).

The CSI includes a Channel Quality Indicator (COI), a Precoding MatrixIndicator (PMI), a Precoding Type Indicator (PTI), and a Rank Indicator(RI). Each of “Indicators” may be denoted as “Indication.”

A Physical Uplink Shared Channel (PUSCH) mainly transmits uplink dataand uplink control data which may also include control data such as CSIand ACK/NACK. Furthermore, the Physical Uplink Shared Channel is alsoused by the terminal device to notify the base station device of uplinkcontrol information as a layer-2 message and layer-3 message in additionto uplink data. Radio resource allocation information on the PhysicalUplink Shared Channel is provided by the Physical Downlink ControlChannel, as in a case of downlink.

An Uplink Reference Signal (also referred to as “uplink pilot signal” or“uplink pilot channel”) includes a Demodulation Reference Signal (DMRS)to be used by the base station device to demodulate the Physical UplinkControl Channel PUCCH and/or Physical Uplink Shared Channel PUSCH, and aSounding Reference Signal (SRS) to be mainly used by the base stationdevice to estimate an uplink channel state. Furthermore, the SoundingReference Signal includes a Periodic Sounding Reference Signal (PeriodicSRS), which is transmitted periodically, or an Aperiodic SoundingReference Signal (Aperiodic SRS), which is transmitted when instructedby the base station device.

A Physical Random Access Channel (PRACH) is a channel used for thenotification (configuration) of a preamble sequence and includes a guardtime. The preamble sequence is constituted of multiple sequences withwhich the base station device is notified of information. For example,when 64 sequences are available, 6-bit information can be provided tothe base station device. The Physical Random Access Channel is used bythe terminal device as a means for accessing the base station device.

The terminal device uses the Physical Random Access Channel to requestan uplink radio resource when no Physical Uplink Control Channel isconfigured or to request the base station device for timing adjustmentinformation (also referred to as Timing Advance (TA)) necessary formatching uplink transmission timing to a reception timing window of thebase station device, for example. Moreover, the base station device canrequest the terminal device to initiate a random access procedure byusing the Physical Downlink Control Channel.

In the uplink, the Common Control Channel CCCH, the Dedicated ControlChannel DCCH, and the Dedicated Traffic Channel DTCH are mapped to theUplink Shared Channel UL-SCH.

The Uplink Shared Channel UL-SCH is mapped to the Physical Uplink SharedChannel PUSCH. The Random Access Channel RACH is mapped to the PhysicalRandom Access Channel PRACH. The Physical Uplink Control Channel PUCCHis used only by the physical channel.

Note that, physical channels or physical signals excluding thosedescribed above do not closely relate to each embodiment of the presentinvention, and therefore detailed descriptions thereof will be omitted.The physical channels or physical signals whose descriptions are omittedinclude a Physical Control Format Indicator CHannel (PCFICH), a PhysicalHybrid ARQ Indicator CHannel (PHICH), a Physical Multicast CHannel(PMCH), and the like.

Furthermore, although, for direct communication between terminal devices(Device to Device or D2D), a logical channel, a transport channel, aphysical channel, or a physical signal (also collectively referred to asa sidelink channel) is also used in EUTRA, descriptions thereof willalso be omitted.

Protocol Stack

As illustrated in FIG. 8, a protocol stack handling control data of theterminal device and the base station device is classified into at leasta physical (PHY) layer, a MAC layer, an RLC layer, a PDCP layer, an RRClayer. Furthermore, as illustrated in FIG. 9, a protocol stack handlinguser data of the terminal device and the base station device isclassified into at least a physical (PHY) layer, a MAC layer, an RLClayer, a PDCP layer. The terminal device and/or the base station devicehas in each layer, an entity which executes the function/role of eachlayer.

The order of the layers in FIG. 8 and FIG. 9 illustrates higher/lowerorder among the layers. For example, the RRC layer is a higher layerthan the PDCP layer, the RLC layer, the MAC layer, and the PHY layer.Furthermore, the MAC layer is a lower layer than the RRC layer, the PDCPlayer, and the RLC layer, and is a higher layer than the PHY layer.

The Physical layer (PHY layer) provides higher layers with a transferservice using the physical channel. The PHY layer is connected to theMedium Access Control layer (MAC layer) with the transport channel. Datamoves between the MAC layer and the PHY layer through the transportchannel. Between the physical layers of the terminal device and the basestation device, data is transmitted and received through the physicalchannel.

The MAC layer is connected to the Radio Link Control layer (RLC layer)with the logical channel. The logical channel is classified, dependingon the type of information to be transmitted, into a control channel fortransmitting control information and a traffic channel for transmittinguser information.

The MAC layer has functions of mapping between the logical channel andthe transport channel, control of the PHY layer for executingDiscontinuous Reception (DRX) and Discontinuous Transmission (DTX),notification of transmit power information, HARQ (error correction)control, handling of a priority between the terminal devices by dynamicscheduling, handling of a logical channel priority, transmission formatselection, and the like. These functions of the MAC layer are executedby the MAC entity.

The RLC layer has functions of transferring data (Protocol Data Unit:PDU) received from a higher layer, an ARQ (error correction) function,segmentation and concatenation of RLC data, PDU re-segmentation, PDUre-ordering, data duplicate detection, protocol error detection, discardof RLC data, and the like. These functions of the RLC layer are executedby the RLC entity.

The Packet Data Convergence Protocol layer (PDCP layer) has functions oftransferring user data or control data, header compression forefficiently transmitting IP packets, i.e., user data, in a radiosection, management of a sequence number, ciphering and deciphering ofuser data or control data, integrity protection of control data, dataduplicate detection and data discard, and the like. These functions ofthe PDCP layer are executed by the PDCP entity.

In the Radio Resource Control layer (RRC layer), only controlinformation is defined. The RRC layer has functions of broadcast ofsystem information (including NAS common information, a cell selectionparameter, neighboring cell information, common channel configuration,Earthquake Tsunami Warning System (ETWS)/Commercial Mobile Alert System(CMAS)), RRC connection control (paging,establishment/modification/release of RRC connection, integrityprotection configuration, ciphering configuration, mobility control,configuration/modification/release of radio bearer (RB), radioconfiguration control (assignment/modification of ARQ configuration,HARQ configuration, DRX configuration, and the like),addition/modification/release of secondary cell, QoS control, recoveryfrom radio link failure), and the like.

Furthermore, the functions of the RRC layer also include inter-RATmobility, typical protocol error handling, measurement configuration andreport, log storage and report, and the like.

There are two types of RBs: a Signaling Radio Bearer (SRB) and a DataRadio Bearer (DRB). The SRB is used as a path over which the layer-3message, i.e., control information, is transmitted. The DRB is used as apath over which user information is transmitted. Between the RRCentities of the base station device and the terminal device, each RB(addition, modification, and release) is configured.

The layer-3 message is a message exchanged between the Radio ResourceControl (RRC) entities of the terminal device and the base stationdevice and handled in a protocol for a Control-plane (C-plane), and maybe used as a synonym of RRC signaling or RRC message. A protocolhandling user data is referred to as “User-plane (UE or U-plane)” incontrast to “Control-plane.”

Random Access Procedure

The random access procedure includes two access procedures: a Contentionbased Random Access procedure and a Non-Contention based Random Accessprocedure. The MAC entity of the terminal device executes the randomaccess procedure.

The Contention based Random Access procedure is a random access whichmay cause contention (collision) of resources between the terminaldevices. The Contention based Random Access procedure is used for, forexample, a scheduling request, in a case of an initial access in a statewhere the terminal device has no connection (communication) with thebase station device, or in a case where uplink data transmission occursin the terminal device in a state where the terminal device has aconnection with the base station device but does not have uplinksynchronization therewith.

The Non-Contention based Random Access procedure is a random access inwhich contention of resources between the terminal devices does notoccur, and is used in a case of a handover, or in a case wheretransmission timing of the terminal device is not valid. In this randomaccess procedure, the terminal device initiates random access inaccordance with an instruction from the base station device.

In the Contention based Random Access procedure, first, the terminaldevice randomly selects one random access preamble (preamble ID) from apreamble group, transmits the selected preamble to the base stationdevice. The base station device which has received the random accesspreamble transmits, to the terminal device, a response to the randomaccess preamble (random access response). The terminal device transmitsa higher layer message on the basis of scheduling information includedin the random access response. The base station device transmits acontention resolution to a terminal device from which the base stationdevice has successfully received the higher layer message.

In the Non-Contention based Random Access procedure, first, the basestation device notifies each terminal device of a preamble ID (orsequence number) and a random access channel number to be used. Theterminal device transmits a random access preamble corresponding to thedesignated preamble ID. The base station device which has received therandom access preamble transmits, to the terminal device, a response tothe random access preamble (random access response). Note that, when avalue of the preamble ID notified from the base station device indicates“0 (zero),” the terminal device performs the Contention based RandomAccess procedure.

Upon detecting the random access preamble transmitted from the terminaldevice, the base station device calculates a shift amount oftransmission timing between the terminal device and the base stationdevice from the random access preamble, assigns one Temporary Cell-RadioNetwork Temporary Identity (Temporary C-RNTI) to the terminal device,maps a Random Access-Radio Network Temporary Identity (RA-RNTI)corresponding to the random access preamble to the Physical DownlinkControl Channel PDCCH, and transmits a random access response includingthe transmission timing information, the scheduling information, theTemporary C-RNTI, and the received random access preamble information(preamble ID) using the Physical Downlink Shared Channel PDSCH.

Upon detecting the corresponding RA-RNTI from the monitored PhysicalDownlink Control Channel PDCCH, the terminal device receives thecorresponding Physical Downlink Shared Channel PDSCH (that is, randomaccess response) on the basis of the scheduling information on thePDCCH. When the random access response includes information on thepreamble ID transmitted by the terminal device, the terminal deviceadjusts uplink transmission timing on the basis of the transmissiontiming information included in the random access response, and transmitsa message including information for identifying the terminal device,such as the C-RNTI (or Temporary C-RNTI and Contention ResolutionIdentity (Contention Resolution ID)), using a radio resource and atransmission format indicated by the scheduling information of therandom access response (also referred to as a message 3).

The base station device receives the message (message 3) transmittedfrom the terminal device, and transmits, to the terminal device,downlink data using the C-RNTI (or Temporary C-RNTI and ContentionResolution ID) included in the received message as a contentionresolution for determining whether or not contention (collision) occursbetween terminal devices using the C-RNTI (or Temporary C-RNTI andContention Resolution Identity). Upon successfully receiving the PDCCHincluding the C-RNTI (or DL-SCH including the Contention Resolution ID),the terminal device may determine that the Contention based RandomAccess procedure has succeeded.

Coverage Enhancement

The terminal device (MTCUE) capable of Coverage Enhancement (supportingCoverage Enhancement) enhances uplink coverage by performing themultiple number of repetitive transmissions across multiple subframeswith respect to a certain transmission to the base station device.Furthermore, the terminal device (MTCUE) capable of the CoverageEnhancement enhances uplink coverage by performing the multiple numberof repetitive receptions across multiple subframes with respect to acertain reception from the base station device.

In other words, in order to compensate for signal attenuation caused bythe Coverage Enhancement, the base station device and the terminaldevice improve reception quality by combining signals across multiplesubframes and receiving the resulting signal.

For example, the base station device may make a notification of thenumber of repetitions of uplink transmission or the number ofrepetitions of downlink reception, or the number of repetitions appliedto both of the transmissions with system information. Furthermore, whentransmitting the random access preamble, the terminal device (MTCUE) mayselect one of the multiple types of numbers of repetitions oftransmission on the basis of either or both of the system informationand measurement quality.

Note that, repetition control with respect to the Physical DownlinkControl Channel PDCCH, the enhanced Physical Downlink Control ChannelEPDCCH, the Physical Uplink Control Channel PUCCH, and the PhysicalRandom Access Channel PRACH may be referred to as repetition, andrepetition control with respect to the Physical Downlink Shared ChannelPDSCH and the Physical Uplink Shared Channel PUSCH may be referred to asbundling.

When the bundling is configured, a bundle size defines the number ofsubframes corresponding to one bundle. Bundling operation (process)relies on an HARQ entity for invoking the same HARQ process for eachtransmission that is part of the same bundle. Within a bundle, HARQretransmissions are non-adaptive and are triggered without waiting forfeedback from previous transmissions depending on the bundle size. TheHARQ feedback of a bundle is only received (HARQ-ACK for the PUSCH) ortransmitted (HARQ-ACK for the PDSCH) for the last subframe of the bundleby the terminal device. The bundling process is performed in the MACentity.

The base station device may configure the multiple numbers ofrepetitions (repetition configurations) corresponding to respectiverepetition levels or bundling sizes. For example, it may be configured(notified) that the number of repetitions is 8 when the repetition level(bundling size) is 1, the number of repetitions is 16 when therepetition level is 2, and the number of repetitions is 32 when therepetition level is 3. The base station device may configure differentvalues (the numbers of repetitions) on the basis of a size oftransmission data. The base station device may configure differentvalues (the numbers of repetitions) for each physical channel.Furthermore, the base station device may configure different values (thenumbers of repetitions) for each logical channel or logical channelgroup. The base station device may notify the terminal device ofinformation on the repetition level or the bundling size, using anindividual RRC message.

The broadcast system information is periodically retransmitted. In thetransmission of the system information, an HARQ retransmission processis performed in the MAC entity. Repetition control on the reception ofthe Physical Downlink Control Channel PDCCH, the reception of theenhanced physical control channel EPDCCH, the transmission of thePhysical Uplink Control Channel PUCCH, and the transmission of thePhysical Random Access Channel PRACH (or random access preamble) isperformed in the PHY

Furthermore, a dedicated Physical Downlink Control Channel for MTCUE(MPDCCH) may be defined. In this case, the MPDCCH may perform a part orall of the role of the PDCCH and/or the EPDCCH to MTCUE.

In light of the above, suitable embodiments of the present inventionwill be described below in detail with reference to the attacheddrawings. Note that, in the description of the embodiments of thepresent invention, when it is determined that a specific description ofa known function or constitution associated with the embodiments of thepresent invention makes the gist of the embodiments of the presentinvention ambiguous, a detailed description thereof will be omitted.

First Embodiment

A first embodiment of the present invention will be described below.

FIG. 1 is a block diagram illustrating an example of a terminal device 1according to the first embodiment of the present invention. The presentterminal device 1 is constituted of at least a reception unit 101, ademodulation unit 102, a decoding unit 103, a reception data controlunit 104, a physical layer control unit 105, a transmission data controlunit 106, a coding unit 107, a modulation unit 108, a transmission unit109, a radio resource control unit 110, a transmit antenna T01, and areceive antenna R01. The “unit” in the drawings, which is expressed as aterm such as a section, a circuit, a constituent device, or a device, isan element that realizes the function and each procedure of the terminaldevice 1.

Note that, hereinafter, the terminal device 1 capable of CoverageEnhancement (supporting Coverage Enhancement) may be described simply asthe terminal device 1. Furthermore, the terminal device 1 may beclassified into two or three types. A first type of terminal device is aterminal classified as one of the existing categories, may be a terminaldevice dedicated to low cost MTC, or may not be a terminal devicededicated to MTC.

Note that, the conventional categories may be constituted of acombination of downlink categories and uplink categories. For example,for the terminal device 1, a category to which the terminal device 1belongs may be indicated by a combination of a certain downlink categoryand a certain uplink category among multiple downlink categories anduplink categories obtained by classification depending on necessarybuffer sizes or the like.

A second type of terminal device a terminal device 1 having a limitationon a system bandwidth supported at least in downlink, in other words,the terminal device 1 supporting a system bandwidth of less than 20 MHz(for example 1.4 MHz). The second type of terminal device may include aterminal device 1 capable of the Coverage Enhancement of a certainrepetition level (bundling size). For example, the terminal device 1capable of only the Coverage Enhancement of repetition level 1 may beclassified as the second type. The second type of terminal device may beclassified as a category (for example, category X) excluding thecategories indicated for the first type of terminal device.

Here, “terminal device capable of the Coverage Enhancement (terminaldevice supporting Coverage Enhancement)” refers to the terminal device 1that is allowed to perform at least a repetitive transmission processand/or a repetitive reception process in accordance with a system, aspecification, or a prescribed rule (regulation, configuration(information element)) notified from a base station device 2; however,it does not matter whether or not the coverage is actually enhanced. Inother words, the terminal device 1 supports various functions newlyadded for the repetitive transmission process and/or the repetitivereception process (for example, some or all of the various procedures(functions) such as a measurement procedure, a cell selection procedure,a cell re-selection procedure, a synchronization, procedure, a pagingprocedure, a system information acquisition procedure, an RRC connectionprocedure, a handover procedure, and a random access procedure).

Likewise, “base station device capable of the Coverage Enhancement (basestation device (cell) supporting the Coverage Enhancement)” refers tothe base station device 2 (cell) that is allowed to perform at least arepetitive transmission process and/or a repetitive reception process inaccordance with a system, a specification, or a prescribed rule(regulation, configuration (information element)) determined between anoperator or the like and the base station device 2; however, it does notmatter whether or not the coverage is actually enhanced. Furthermore,the base station device 2 (cell) supports various functions newly addedto the terminal device 1 for the repetitive transmission process and/orthe repetitive reception process (for example, some or all of thevarious procedures (functions) such as the measurement procedure, thecell selection procedure, the cell re-selection procedure, thesynchronization procedure, the paging procedure, the system informationacquisition procedure, the RRC connection procedure, the handoverprocedure, and the random access procedure, and the like).

A third type of terminal device is the terminal device 1 supporting theCoverage Enhancement of all repetition levels (bundling sizes). Thethird type of terminal device may be classified as a category (forexample, category Y) excluding the categories indicated for the firsttype and second type of terminal devices. In other words, the maximumnumber of repetitions supported by the second type of terminal devicemay be less than that supported by the third type of terminal device.Each type may support different functions, and usage thereof may not belimited to MTC (MTC service). In other words, even when thisspecification describes MTCUE, the usage thereof is not limited to MTC.

The radio resource control unit 110 executes each function of the RRCentity which performs radio resource control of the terminal device 1.Furthermore, the reception data control unit 104 and the transmissiondata control unit 106 execute respective functions of the MAC entity,the RLC entity, and the PDCP entity in a data link layer (layer 2).

Here, the MAC entity has the function of making notification of the dataamount in a transmission buffer corresponding to each logical channel(Buffer Status Report (BSR)), and the function of performing a radioresource request for transmitting uplink data (Scheduling Request). Whentransmission data is present in a higher layer of the MAC entity and anuplink resource is not allocated to the terminal device 1 (for example,at initial access), the MAC entity executes the random access procedurefor the scheduling request

Furthermore, when carrier aggregation that allows for communicationusing multiple cells is performed, the MAC entity controls the physicallayer for performing activation/deactivation of a cell and for managingan uplink transmission timing.

Note that, in order to simultaneously/concurrently perform the receptionprocess and the transmission process at multiple frequencies (frequencyband, frequency bandwidth) or in the same subframe of a certain cell,the terminal device 1 may include multiple elements of some or all ofthe reception system blocks (the reception unit 101, the demodulationunit 102, the decoding unit 103, the receive antenna R01), multiplefrequencies (frequency band, frequency bandwidth), and transmissionsystem blocks (the coding unit 107, the modulation unit 108, thetransmission unit 109, the transmit antenna T01).

As for the reception process in the terminal device 1, from the radioresource control unit 110, reception data control information is inputto the reception data control unit 104, and physical layer controlinformation, i.e., a control parameter for controlling each block, isinput to the physical layer control unit 105. The physical layer controlinformation includes a parameter configuration that is constituted ofreception control information and transmission control information andis necessary for radio communication control of the terminal device 1.

The physical layer control information is configured by a radio resourceconnection configuration, cell-specific system information, systemparameter, or the like that is dedicatedly transmitted from the basestation device 2 to the terminal device 1, and is input to the physicallayer control unit 105 by the radio resource control unit 110 asnecessary. The physical layer control unit 105 suitably inputs thereception control information, i.e., control information relating to thereception, to the reception unit 101, the demodulation unit 102, and thedecoding unit 103.

The reception control information may include, as downlink schedulinginformation, information such as reception frequency band information,reception timing relating to the physical channel and the physicalsignal, a multiplexing method, Radio Resource Control information, andthe like. Furthermore, the reception data control information isdownlink control information including secondary cell deactivation timerinformation, DRX control information, multicast data receptioninformation, downlink re-transmission control information, controlinformation relating to repetitive reception, and the like, and includescontrol information relating to the downlink in each of the MAC layer,the RLC layer, and the PDCP layer.

A receive signal is received in the reception unit 101 through thereceive antenna R01. The reception unit 101 receives a signal from thebase station device 2 (or other nodes including the terminal device 1)at the frequency and in the frequency band notified with the receptioncontrol information. The received signal is input to the demodulationunit 102. The demodulation unit 102 demodulates the signal. Thedemodulation unit 102 inputs the demodulated signal to the decoding unit103.

The decoding unit 103 decodes the input signal, and inputs each piece ofdecoded data (also referred to as downlink data and downlink controldata, a downlink transport block (TB), or a downlink protocol data unit(PDU)) to the reception data control unit 104. Furthermore, a MACcontrol element (MAC-CE) transmitted from the base station device 2together with each piece of data is also decoded in the decoding unit103, and related data is input to the reception data control unit 104.

The reception data control unit 104 performs control of the physicallayer control unit 105 (for example, cell activation/deactivation, DRXcontrol, transmission timing adjustment, or the like) based on thereceived MAC control element, and buffers each piece of decoded data toperform error correction control of retransmitted data (HARQ). Relateddata among each piece of data input to the reception data control unit104 is input (transferred) to the radio resource control unit 110.

Furthermore, the reception data control unit 104 adjusts receptiontiming of the terminal device 1 (frame synchronization, subframesynchronization, symbol synchronization, or the like) from receptiontiming of a synchronization signal received by the reception unit 101 orthe like. The reception timing is managed in the physical layer controlunit 105 and is fed back to the reception unit 101 or the transmissionunit 109 such that downlink synchronization and/or uplinksynchronization is appropriately adjusted.

Furthermore, the reception data control unit 104 may measure receptionquality of the downlink reference signal, which is a signal of a knownsequence (RSRP, RSSI, RSRQ, or the like), and report the result to theradio resource control unit 110. A measurement period of the receptionquality may be configured on the basis of the repetition configuration,or may be notified or broadcast with the RRC message from the basestation device 2. The radio resource control unit 110 may determine thenumber of repetitions of the transmission for the Coverage Enhancementon the basis of the reported reception quality.

Furthermore, as for the transmission process of the terminal device 1,from the radio resource control unit 110, transmission data controlinformation is input to the transmission data control unit 106, andphysical layer control information, i.e., a control parameter forcontrolling each block, is input to the physical layer control unit 105.The physical layer control unit 105 suitably inputs the transmissioncontrol information, i.e., control information relating to thetransmission, to the coding unit 107, the modulation unit 108, and thetransmission unit 109.

The transmission control information includes, as uplink schedulinginformation, information such as coding information, modulationinformation, transmission frequency band information, timing information(or TA) relating to the physical channel and the physical signal, themultiplexing method, radio resource allocation information, and thelike.

Furthermore, the transmission data control information is the uplinkcontrol information including DTX control information, random accessconfiguration information, uplink shared channel information, logicalchannel priority information, resource request configurationinformation, cell group information, uplink re-transmission controlinformation, the buffer status report, control information relating torepetitive transmissions, and the like. The radio resource control unit110 may configure multiple pieces of random access configurationinformation individually corresponding to multiple cells in thetransmission data control unit 106.

Furthermore, the radio resource control unit 110 manages timingadjustment information and a transmission timing timer used foradjustment of the uplink transmission timing, and manages an uplinktransmission timing state (transmission timing adjusted state ortransmission timing non-adjusted state) for each cell (or each cellgroup, each TA group). The timing adjustment information and thetransmission timing timer are included in the transmission data controlinformation.

Note that, in a case where multiple uplink transmission timing statesneed to be managed, the transmission data control unit 106 manages thetiming adjustment information corresponding to the uplink transmissiontiming of each of the multiple cells (or cell group, TA group). Theresource request configuration information includes at least maximumtransmission counter configuration information and radio resourcerequest prohibition timer information. The radio resource control unit110 may configure multiple pieces of resource request configurationinformation individually corresponding to multiple cells in thetransmission data control unit 106.

The transmission data occurring in the terminal device 1 (also referredto as uplink data and uplink control data, an uplink transport block(TB), or an uplink protocol data unit (PDU)) is input from the radioresource control unit 110 (or a higher layer unit such as a non-accessstratum layer unit (not illustrated)) to the transmission data controlunit 106 at a desired timing. Note that, the transmission data isprocessed, in each layer, by respective units of an RRC PDU, a PDCP PDU,an RLC PDU, and an MAC PDU. At this time, the transmission data controlunit 106 calculates the input transmission data amount (uplink bufferedamount). Furthermore, the transmission data control unit 106 has thefunction of determining whether the input transmission data belongs tothe Control-plane or belongs to the User-plane.

Furthermore, when having the transmission data input thereto, thetransmission data control unit 106 stores the transmission data in anuplink buffer (not illustrated) in the transmission data control unit106. Furthermore, the transmission data control unit 106 performsmultiplexing and assembling on the basis of, for example, a priority ofthe transmission data stored in the uplink buffer to create the MAC PDU.The transmission data control unit 106, then determines whether or not aradio resource necessary for transmission of the input transmission datais allocated to the terminal device 1.

The transmission data control unit 106, on the basis of the radioresource allocation, selects either the radio resource request using thePhysical Uplink Shared Channel PUSCH and the Physical Uplink ControlChannel (SR-PUCCH) or the radio resource request using the PhysicalRandom Access Channel, and requests, to the physical layer control unit105, the control process for transmitting the selected channel.

Here, the transmission data control unit 106 creates the buffer statusreport on the basis of the input transmission data. In other words, thetransmission data control unit 106 creates the buffer status reportbased on the buffered amount of normal transmission data as the MACcontrol element.

Furthermore, the transmission data control unit 106 may configure thenumber of repetitions of the transmission of the terminal device itselfon the basis of the repetition configuration input from the radioresource control unit 110. The number of repetitions may be configuredby the physical channel unit, or the logical channel (logical channelgroup) unit.

Furthermore, in accordance with the transmission control information,the coding unit 107 suitably codes each piece of data, and inputs thepiece of coded data to the modulation unit 108. The modulation unit 108performs a suitable modulation process on the basis of a channelstructure for transmitting each piece of coded data. The transmissionunit 109 maps each piece of modulated data to the frequency domain,converts a signal in the frequency domain to a signal in the timedomain, and performs power amplification by superimposing the signal ona carrier wave with a prescribed frequency. In accordance with thetiming adjustment information on each cell (or each cell group, each TAgroup) input from the radio resource control unit 110, the transmissionunit 109 further adjusts the uplink transmission timing and transmitsthe signal through the transmit antenna T01.

The Physical Uplink Shared Channel to which the uplink control data isallocated can also include the layer-3 message (Radio Resource Controlmessage; RRC message), for example, in addition to the user data.

In FIG. 1, although other constituent elements of the terminal device 1and other transmission paths of data (control information) between theconstituent elements are omitted, it is apparent that the terminaldevice 1 includes multiple blocks having other functions necessary foroperating as the terminal device 1 as constituent elements. For example,in the higher layer of the radio resource control unit 110, a Non AccessStratum (NAS) layer unit which performs control with a core network andan application layer unit are present.

FIG. 2 is a block diagram illustrating an example of the base stationdevice 2 according to the first embodiment of the present invention. Thepresent base station device is constituted of at least a reception unit201, a demodulation unit 202, a decoding unit 203, a reception datacontrol unit 204, a physical layer control unit 205, a transmission datacontrol unit 206, a coding unit 207, a modulation unit 208, atransmission unit 209, a radio resource control unit 210, a networksignal transmission and reception unit 211, a transmit antenna T02, anda receive antenna R02. The “unit” in the drawings, which is expressedalso with a term such as a section, a circuit, a constituent device, ora device, is an element that realizes the function and each procedure ofthe base station device 2.

The radio resource control unit 210 executes each function of the RRCentity which performs the radio resource control of the base stationdevice 2. Furthermore, the reception data control unit 204 and thetransmission data control unit 206 execute respective functions of theMAC entity, the RLC entity, and the PDCP entity of the data link layer(layer 2).

Note that, in order to support the transmission and reception processesat multiple frequencies (frequency band, frequency bandwidth) for thecarrier aggregation or the like or in the same subframe of the cell, thebase station device 2 may include multiple elements of some or all ofthe reception system blocks (the reception unit 201, the demodulationunit 202, the decoding unit 203, the receive antenna R02), multiplefrequencies (frequency band, frequency bandwidth), and the transmissionsystem blocks (the coding unit 207, the modulation unit 208, thetransmission unit 209, the transmit antenna R02).

The radio resource control unit 210 inputs downlink data and downlinkcontrol data to the transmission data control unit 206. When the MACcontrol element to be transmitted to the terminal device 1 is present,the transmission data control unit 206 inputs the MAC control elementand each piece of data (downlink data or downlink control data) to thecoding unit 207.

Furthermore, the transmission data control unit 206 may configure thenumber of repetitions of the transmission of the base station deviceitself on the basis of the repetition configuration input from the radioresource control unit 210. The number of repetitions may be configuredby the physical channel unit, or the logical channel (logical channelgroup unit).

Furthermore, the coding unit 207 codes the input MAC control element andeach piece of data, and inputs the result to the modulation unit 208.The modulation unit 208 modulates the coded signal. The signal modulatedin the modulation unit 208 is input to the transmission unit 209. Aftermapping the input signal to the frequency domain, the transmission unit209 converts the signal in the frequency domain to a signal in the timedomain, performs power amplification by superimposing the signal on acarrier wave with a prescribed frequency, and transmits the signalthrough the transmit antenna T02. The Physical Downlink Shared Channelto which the downlink control data is allocated typically constitutesthe layer-3 message (RRC message).

Furthermore, the reception unit 201 converts the signal received fromthe terminal device 1 through the receive antenna R02 to a digitalsignal in a baseband. In a case where cells with multiple differenttransmission timings are configured for the terminal device 1, thereception unit 201 receives signals at different timings for each cell(or each cell group, each TA group). The digital signal obtained by theconversion in the reception unit 201 is input to and demodulated in thedemodulation unit 202. The signal obtained by the demodulation in thedemodulation unit 202 is subsequently input to the decoding unit 203.

The decoding unit 203 decodes the input signal, and inputs each piece ofdecoded data (uplink data and uplink control data) to the reception datacontrol unit 204. Furthermore, the MAC control element transmitted fromthe terminal device 1 together with each piece of data is also decodedin the decoding unit 203, related data is input to the reception datacontrol unit 204.

The reception data control unit 204 performs control of the physicallayer control unit 205 (for example, control relating to a powerheadroom report, control relating to the buffer status report, or thelike) based on the received MAC control element, and buffers each pieceof decoded data to perform error correction control of retransmitteddata (HARQ). Each piece of data input to the reception data control unit204 is input (transferred) to the radio resource control unit 210 asnecessary.

Furthermore, when the buffer status report from the terminal device 1 isinput from the decoding unit 203, the reception data control unit 204determines either the radio resource request for communication with thebase station device itself or the radio resource request for datacommunication between devices, and configures the radio resource to beallocated to the terminal device 1.

Furthermore, the reception data control unit 204 may measure receptionquality of the Uplink Reference Signal and report the result to theradio resource control unit 210. The radio resource control unit 210 maydetermine the number of repetitions of the transmission of the terminaldevice 1 for the Coverage Enhancement on the basis of the reportedreception quality.

The physical layer control information necessary for control of eachblock includes a parameter configuration that is constituted of thereception control information and the transmission control informationand is necessary for the radio communication control of the base stationdevice 2. The physical layer control information is configured by ahigher network device (MME, gateway device (SGW), OAM, or the like) orwith the system parameter, and is input by the radio resource controlunit 210 to the control unit 204 as necessary.

The physical layer control unit 205 inputs the physical layer controlinformation associated with the transmission to each of the blocks, thatis, the coding unit 207, the modulation unit 208, and the transmissionunit 209 as the transmission control information, and suitably inputsthe physical layer control information associated with the reception toeach of the blocks, that is, the reception unit 201, the demodulationunit 202, and the decoding unit 203 as the reception controlinformation.

The reception data control information includes control informationrelating to the uplink of the terminal device 1 for each of the MAClayer, the RLC layer, and the PDCP layer of the base station device 2.Furthermore, the transmission data control information includes controlinformation relating to the downlink of the terminal device 1 for eachof the MAC layer, the RLC layer, and the PDCP layer of the base stationdevice 2. In other words, the reception data control information and thetransmission data control information are configured for each terminaldevice 1.

Furthermore, the radio resource control unit 210 configures, on thebasis of a measurement report message from the terminal device 1 and/oruplink reception quality information from the reception data controlunit 204, information on the number of repetitions of the transmissionor the reception (the number of repetitive receptions, the number ofrepetitive transmissions). In other words, the radio resource controlunit 210 configures, for each terminal device 1, the number ofrepetitions of the downlink reception of the terminal device 1 and thenumber of repetitions of the uplink transmission of the terminal device1. The number of repetitions may be configured commonly for the uplinkand the downlink, may be configured independently for the uplink and thedownlink, or may be configured for each physical channel.

The radio resource control unit 210 creates the RRC message includingthe above-described number of repetitions as an information element, andoutputs the message to the reception data control unit 204. Furthermore,the radio resource control unit 210 notifies the physical layer controlunit 205 of the number of repetitions of the reception and/or the numberof repetitions of the transmission configured for the terminal device 1.The RRC message may be an RRC reconfiguration message, or may be a newRRC message, for example.

The network signal transmission and reception unit 211 transmits(transfers) or receives the control message or the user data between thebase station devices 2 or between the higher network device (DAME, SGW)and the base station device 2. In FIG. 2, although other constituentelements of the base station device 2 and other transmission paths ofdata (control information) between the constituent elements are omitted,it is apparent that the base station device 2 includes multiple blockshaving other functions necessary for operating as the base stationdevice 2 as constituent elements. For example, a radio resourcemanagement unit and an application layer unit are present above theradio resource control unit 210.

A case where the RRC connection establishment procedure is executed whenthe terminal device 1 changes from the RRC idle state to the RRCconnected state will be described.

The terminal device 1 acquires system information from a selectedserving cell in the RRC connection establishment procedure, and executesthe random access procedure on the basis of a common radio resourceconfiguration included in the acquired system information as aninformation element.

At this time, some or all of the parameters used by the terminal device1 for the RRC connection establishment procedure and necessary for therandom access procedure may be provided via the common radio resourceconfiguration included in system information (for example, Systeminformation Block Type 2, SIB2) for all the terminal devices 1 (that is,the first to third types of terminal devices), may be provided via thecommon radio resource configuration included in system information (forexample, System information Block Type 20, SIB20) for the terminaldevices 1 capable of the Coverage Enhancement (that is, the second andthird types of terminal devices), or may be provided being included inboth the pieces of system information.

Furthermore, UE timer And Constants configuration (hereinafter, referredto as timer/constants configuration) of the terminal device relating tothe RRC connection establishment procedure used in the terminal device 1included in first system information and/or second system informationmay be provided (transmitted).

System information including the common radio resource configuration andthe timer/constants configuration as information elements for all theterminal devices 1 is referred to as the first system information.Furthermore, system information including the common radio resourceconfiguration and the timer/constants configuration as informationelements for the terminal device 1 capable of the Coverage Enhancementis referred to as the second system information.

The common radio resource configuration included in the first systeminformation is referred to as a first common radio resourceconfiguration, the common radio resource configuration included in thesecond system information is referred to as a second common radioresource configuration. The timer/constants configuration included inthe first system information is referred to as a first timer/constantsconfiguration, the timer/constants configuration included in the secondsystem information is referred to as a second timer/constantsconfiguration.

Here, the second system information is system information repetitivelytransmitted at certain short intervals (for example, by subframe unit),and is system information that the terminal device 1 capable of theCoverage Enhancement can acquire by means of repetitive reception.

When new system information (second system information, for example, theSIE320) is used, the system information may include at least one of thefollowing characteristics: (1) transmitted in a contiguous bandwidth ofnot more than 6 RB (narrowband);

(2) subjected to bundling (repetition) and transmitted from the basestation device 2;

(3) not require the PDCCH or the EPDCCH (not being scheduled with PDCCHor EPDCCH);

(4) scheduled via the PDCCH or the EPDCCH allocated to a differentregion (search space);

(5) scheduled with the PDCCH or EPDCCH in a narrowband;

(6) having a modulation and coding scheme designated with other systeminformation (for example, MIB/S1131) or system parameters;

(7) having a longer modification period than before;

(8) able to be used only in the second and third types of terminaldevices; and

(9) considered as essential system information in the second and thirdtypes of terminal devices.

The terminal device 1, which is not capable of the Coverage Enhancement,may perform the random access by using a random access parameter (firstparameter) included in the first common radio resource configuration,and the terminal device 1, which is capable of the Coverage Enhancement,may perform the random access by using a new random access parameter(second parameter) relating to the Coverage Enhancement included in thesecond common radio resource configuration.

At this time, multiple sets of random access parameters corresponding tothe number of repetitions (repetition level or bundling size) may beincluded in the second common radio resource configuration, or some ofthe random access parameters may be included in the second common radioresource configuration. For example, the base station device 2 (cell)supporting one to three times as the number of repetitions transmits aset of three types of parameters (random access parameters) relating tothe random access with the parameters included in the common secondradio resource configuration.

The terminal device 1 may perform random access resource selection onthe basis of the random access parameter corresponding to the number ofrepetitions. In other words, the number of repetitions (or repetitionlevel) and a random access resource in the coverage enhanced cell may bemapped on one-to-one basis. Here, the random access resource selected bythe terminal device 1 includes at least the random access preamblegroup, the subfrarne for transmitting the random access preamble, andthe frequency resource allocation of the uplink and a frequency hoppingpattern may further be selected as the random access resource.

When multiple sets of the random access parameters are configured forthe second common radio resource configuration, the terminal device 1may select one corresponding parameter (parameter set) on the basis ofthe measurement result (RSRP and/or RSRQ) on the cell. In other words,the terminal device 1 may determine the number of repetitions(repetition level) on the basis of the measurement result on the celland perform random access resource selection on the basis of theparameter (or parameter set) corresponding to the number of repetitions(repetition level).

Furthermore, the terminal device 1 may select a corresponding parameter(parameter set) on the basis of UE capability. The UE capability of theterminal device 1 to be considered here includes, for example,capability information on the physical layer such as the maximum numberof repetitions supported by the terminal device 1, capabilityinformation relating to types (first to third types) of the terminaldevice 1, other capability information indicating whether or not theterminal device 1 supports mobility (that is, a procedure involving acell change such as cell reselection or a handover) (or whether or notthe terminal device 1 is a movable terminal device), and the like.

A condition required for the measurement of the terminal device 1capable of the Coverage Enhancement may be moderate in comparison with acondition required for the measurement of the normal terminal device 1(also referred to as normal coverage UE).

Furthermore, multiple UE timers (also referred to as an RRC timer)individually corresponding to the numbers of repetitions (or repetitionlevels) and/or constant configuration may be included in the secondtimer/constants configuration. In other words, a cell supporting one tothree times as the number of repetitions has three sets of UE timersand/or constant configurations.

The UE timers included in the second timer/constants configuration are,for example, T300, T301, T310, and T311. Furthermore, constants includedin the second timer/constants configuration are, for example, N310 andN311. The T300 is a timer used in the RRC connection establishmentprocedure, the T301 is a timer used in an RRC connectionre-establishment procedure, the T310 is a timer used in radio linkfailure detection, and the T311 is a timer used in cell search after theradio link failure detection. The N310 is a constant that is asynchronization primitive and indicates the maximum count number ofin-sync indication, the N311 is a constant that is a synchronizationprimitive and indicates the maximum count number of out-of-syncindication.

FIG. 3 is a flowchart diagram for explaining an example of a UE timerselection process in the RRC connection establishment procedure of theterminal device 1 capable of the Coverage Enhancement.

The base station device 2 repetitively transmits the second systeminformation on the cell where the Coverage Enhancement is performed.Furthermore, the base station device 2 transmits the second systeminformation that includes at least the second common radio resourceconfiguration and the second timer/constants configuration. Note that,the second system information may also be considered as a TB (MAC PDU)including the BCCH (BCH or SIB) corresponding to the second systeminformation.

For example, the base station device 2 performs repetitive (bundling)transmissions of a certain number of repetitions (for example, 30 times)of the second system information. Alternatively, the base station device2 performs repetitive transmissions of the second system information.

The terminal device 1 attempts the reception (acquisition) of the secondsystem information repetitively transmitted on the cell in step S101. Inother words, the terminal device 1 attempts acquisition of the secondsystem information by repeating the reception process for the secondsystem information. At this time, the terminal device 1 acquires atleast the second common radio resource configuration and the secondtimer/constants configuration from the received second systeminformation.

Subsequently, the terminal device 1 determines the repetition level instep S102. The repetition level in the terminal device 1 can bedetermined (selected) by using any of: (1) a common repetition levelindicated by the second system information;

(2) a repetition level determined in the random access resourceselection on the basis of the measurement result;

(3) a repetition level determined on the basis of the capabilityinformation on the terminal device 1; and

(4) a repetition level notified (allocated) from the base station device2 during the random access procedure.

Note that, the base station device 2 can transmit the maximum value ofthe repetition level, which is applicable to the terminal device 1 onthe cell, included in the system information for each cell. Furthermore,when the maximum value of the repetition level is not designated, theterminal device 1 may use a default value or the maximum value of therepetition level supported by the terminal device 1 as the maximum valueof the repetition level of the cell.

Note that, when the base station device 2 makes notification(configuration, indication) of the repetition level during the randomaccess procedure (in the case of (4) described above), at least therepetition level applied to the transmission of the random accesspreamble needs to be determined (selected) by the terminal device 1. Theterminal device 1 applies the repetition level indicated by the basestation device 2 to the transmission and the reception after the message3. Note that, any method of (1) to (3) described above can be used forthe determination method of the repetition level in the terminal device1.

The repetition level indicated by the base station device 2 may benotified with the MAC control element in the random access response, maybe indicated by the random access response (DL-SCH), or may be indicatedby the physical layer downlink control information notified on the PDCCHor the EPDCCH. Alternatively, the repetition level may be implicitlynotified by the subframe number and/or the frequency resource in whichthe random access response is transmitted. The repetition level may beseparately configured for the uplink and the downlink. Furthermore, therepetition level may be notified with the MAC control element in thecontention resolution, or indicated by contention resolution (DL-SCH).

When the random access resource used for the detected random accesspreamble is a resource relating to the Coverage Enhancement on the cell,the base station device 2 may determine a transmission frequency of therandom access response and/or the number of transmissions (repetitionlevel) of the random access response on the basis of the random accessresource.

In other words, the base station device 2 may determine a transmissionresource of the random access response on the basis of the random accesspreamble transmitted from the terminal device 1 and/or the frequencywith which the random access preamble is received. The base stationdevice 2 may not transmit the PDCCH or the EPDCCH for scheduling therandom access response. The terminal device 1 may directly monitor therandom access response without monitoring the PDCCH or the EPDCCH. Theterminal device 1 may determine the transmission frequency of the randomaccess response and/or the repetition level of the random accessresponse on the basis of the selected random access resource, and maymonitor the random access response.

Subsequently, the terminal device 1 configures the timer (UE timer) usedfor the RRC connection establishment procedure (step S103). The terminaldevice 1 uses the timer 7300 as the UE timer for the RRC connectionestablishment procedure. The timer T300 may use a value indicated by thesecond timer/constants configuration included in the second systeminformation (A1); may he configured on the basis of the repetition leveldetermined in step S102 (B1); or may be configured as a value obtainedby totaling configuration values of a reference time (T300reference) andan offset time (T300offset). Hereinafter, the UE timer used for the RRCconnection establishment procedure on the coverage enhanced cell, inorder to distinguish from the conventional timer T300, is referred to asa timer T308 (also referred to as a timer T300bis).

In other words, the base station device 2 may indicate, to the terminaldevice 1, a value of the timer T308 by the second timer/constantsconfiguration included in the second system information; may notify theterminal device 1 of values of multiple timers T308 based on therepetition level (B2); and may notify the terminal device 1 of thereference time (T308reference) and the offset time (T308offset) forcalculating the timer T308 C2).

In (A1/A2) described above, it is preferable that a value of the timerincluded in the second system information be configurable such that themaximum time is longer than the value of the first timer/constantsconfiguration. For example, when as the timer T300 (first timer)notified with the first timer/constants configuration, any valueincluding 100 ms, 200 ms, 300 ms, 400 ms, 500 ms, 600 ms, 1000 ms, and2000 ms can be configured, it is preferable that, as the timer T308(second timer) notified with the second timer/constants configuration,any value including 500 ms, 1000 ms, 2000 ms, 3000 ms, 5000 ms, 10000ms, 15000 ms, and 20000 ms be configurable.

Alternatively, in (A1/A2) described above, the value of the secondtimer/constants configuration included in the second system informationmay be a value in a different range from the value of the firsttimer/constants configuration included in the first system information,and furthermore may always exceed a value range configurable for thefirst timer/constants configuration. For example, when as the timer T300(first timer) notified with the first timer/constants configuration, anyvalue including 100 ms, 200 ms, 300 ms, 400 ms, 500 ms, 600 ms, 1000 ms,and 2000 ms can be configured, it is preferable that, as the timer T308(second timer) notified with the second timer/constants configuration,any value including 3000 ms, 4000 ms, 5000 ms, 6000 ms, 10000 ms, 15000ms, 20000 ms, and 30000 ms be configurable.

Furthermore, in (B1/B2) described above, for a cell in which therepetition levels 1 to 3 are selected, three different values of thetimer T308 (second timer) individually corresponding to the repetitionlevels may be prepared (transmitted). For example, when the repetitionlevel is 1, the terminal device 1 may select the timer T308corresponding to the repetition level 1 from the second timer/constantsconfiguration and use the timer T308. The base station device 2 maytransmit, to the terminal device 1, the second timer included in thesecond system information, or may transmit with a dedicated RRC message.

Furthermore, in (C1/C2) described above, the offset time (T308offset)may be configured on the basis of the repetition level determined instep S102. In other words, for a cell in which the repetition levels 1to 3 are selected, three different values of the offset timeindividually corresponding to the repetition levels may be prepared(transmitted). For example, when the repetition level is 1, the terminaldevice 1 may select the offset time (T308offset-lv1) corresponding tothe repetition level 1 from the second timer/constants configuration anduse the offset time.

Alternatively, in (C1/C2) described above, the offset time (T308offset)may be calculated using a multiple (coefficient) based on the repetitionlevel determined in step S102. In other words, for a cell in which therepetition levels 1 to 3 are selected, three different multiplesindividually corresponding to the repetition levels are prepared(transmitted), the terminal device 1 may multiply the multiple selectedon the basis of the repetition level by the reference time(T308reference) to calculate the UE timer.

For example, when the reference time (T308reference) is 500 ms and therepetition level is 1, the terminal device 1 selects the multiplecorresponding to the repetition level 1 from the second timer/constantsconfiguration (for example, 2), calculates the timer T308 from thereference time and the corresponding multiple, and uses the timer T308.In the present example, the value of the timer 1308 is 500*2=1000 ms.Alternatively, the repetition level may indicate the multiple as it is.Furthermore, the base station device 2 may configure a different valuefor each cell as the reference time.

The base station device 2 may transmit, to the terminal device 1, thereference time and the offset time (or multiple) included in the secondsystem information, or may transmit using the dedicated RRC message.

When the timer T308 (second timer) acquired from the second systeminformation is used as in (A1/A2) described above, the terminal device 1may create an RRC connection request message in the RRC connectionestablishment procedure and provide (submit) the message to the lowerlayer after starting the timer T308.

On the other hand, when the timer T308 (second timer) based on therepetition level is used as in (B1/B2) and (C1/C2) described above, therandom access procedure is initiated after the RRC connection requestmessage is provided (submitted) from the RRC entity of the terminaldevice 1 to the lower layer (for example, PDCP entity or RLC entity) ofthe terminal device 1. Therefore, the terminal device 1 (RRC entity),after receiving the information (indication) relating to the repetitionlevel from the lower layer, needs to start the timer T308 based on thereceived repetition level. This will be described with reference to FIG.4 and FIG. 5.

FIG. 4 is a flowchart diagram for explaining an example of a UE timerstart process in the RRC connection establishment procedure of theterminal device 1 capable of the Coverage Enhancement. FIG. 4illustrates an example of a case where an indication is transmitted tothe higher layer of the terminal device 1 (for example, RRC entity) whenthe MAC entity of the terminal device 1 initiates the random accessprocedure.

In FIG. 4, the terminal device 1 determines the repetition level beforeinitiating the random access procedure for the cell capable of theCoverage Enhancement. As for a determination method of the repetitionlevel, any of the methods in step S102 may be used. The terminal device1 (RRC entity) provides (submits) the RRC connection request message tothe lower layer. The MAC entity of the terminal device 1 initiates therandom access procedure in order to transmit the RRC connection requestmessage (step S202). The MAC entity of the terminal device 1 during therandom access procedure transmits the indication indicating therepetition level to the higher/upper layer (for example, RRC entity) ofthe terminal device 1 (step S203).

For example, when the terminal device 1 selects the (temporary)repetition level for transmitting the random access preamble, the MACentity of the terminal device 1 transmits the indication to the higherlayer of the terminal device 1. Furthermore, for example, when therepetition level is notified (indicated) from the base station device 2during the random access procedure, the MAC entity of the terminaldevice 1 transmits the indication to the higher layer of the terminaldevice 1. Here, the indication includes at least the repetition level ofthe terminal device 1 on the cell or information indicating therepetition level.

In other words, in step S203, the terminal device 1 (RRC entity)receives the indication including the repetition level information fromthe tower layer when initiating the random access procedure (whenperforming the random access resource selection) or during the randomaccess procedure.

The terminal device 1 (RRC entity) which has received the indicationdetermines the value of the timer T308 as the timer (UE timer) relatingto the RRC connection establishment procedure on the basis of therepetition level, and starts the operation of the timer T308 (stepS204).

FIG. 5 is a flowchart diagram for explaining another example of the UEtimer start process in the RRC connection establishment procedure of theterminal device 1 capable of the Coverage Enhancement. Step S301 andstep S302 in FIG. 5 have the same operations as those in step S201 andstep S202 in FIG. 4, respectively, and thus descriptions thereof will beomitted.

In step S303, the MAC entity of the terminal device 1 determines whetheror not the random access procedure has succeeded. When the random accessprocedure has succeeded (Yes in step S303), the MAC entity of theterminal device 1 transmits the indication indicating the repetitionlevel to the higher/upper layer (for example, RRC entity) of theterminal device 1 (step S304). On the other hand, when the random accessprocedure has yet to succeed (No in step S303), the MAC entity of theterminal device 1 repeats the process until the random access proceduresucceeds.

In other words, in step S304, the terminal device 1 (RRC entity)receives, from the lower layer, the indication including the repetitionlevel information when the random access procedure has succeeded.

Note that, in order to prevent deadlock when the lower layer does notnotify the terminal device 1 of the indication, the terminal device 1(RRC entity) may start another UE timer acquired from the second systeminformation or the MAC timer in step S302. When the UE timer(hereinafter, referred to as T309) is used, after the RRC connectionrequest message is created or when the RRC connection request message isprovided (submitted) to the lower layer, the T309 is started. When theMAC timer (hereinafter, referred to as a CE-RACH timer) is used, theCE-RACH timer is started from an initial transmission subframe of therandom access preamble.

When the timer T309 has expired, the terminal device 1 (RRC entity) maydetermine that the RRC connection establishment procedure fails.Furthermore, when receiving the indication from the lower layer (stepS304 in FIG. 5), the terminal device 1 (RRC entity) may stop the timerT309 and start the timer T308.

Furthermore, when the CE-RACH timer has expired, the terminal device 1(MAC entity) may determine that the random access procedure fails.Furthermore, when the random access procedure has succeeded, theterminal device 1 (MAC entity) may stop the CE-RACH timer (step S303 inFIG. 5).

The terminal device 1 (RRC entity) which has received the indicationfrom the lower layer determines the timer T308 as the timer (UE timer)relating to the RRC connection establishment procedure on the basis ofthe indicated repetition level, and starts the operation of the timerT308 (step S305 in FIG. 5). Furthermore, when the timer T308 hasexpired, the terminal device 1 (RRC entity) may determine that the RRCconnection establishment procedure fails.

Although FIG. 4 and FIG. 5 illustrate an example of a case wheredifferent UE timers are configured on the basis of the repetition levelof the terminal device 1, as in (A1/A2) described above, by configuringthe UE timer for long period compliant with the Coverage Enhancement,start timing of the UE timer may be set in the same manner as in theconventional terminal device 1. However, the timer value in this case isnot determined (configured) corresponding to the repetition level of theterminal device 1, time until the UE timer expires may increase morethan necessary. FIG. 6 is a diagram for explaining a method in which theterminal device 1 capable of the Coverage Enhancement aborts (halts) theRRC procedure, as for this increase in time until expiration.

In FIG. 6, the terminal device 1 starts the UE timer (step S401). Atthis time, the terminal device 1 may start the timer T308 relating tothe RRC connection establishment procedure acquired from the secondtimer/constants configuration included in the second system information.

Subsequently, the MAC entity of the terminal device 1 initiates therandom access procedure as one procedure in the RRC connectionestablishment procedure (step S402). The MAC entity of the terminaldevice 1 monitors a response to the transmission data relating to therandom access transmitted most recently in step S403.

In other words, when the transmission data that the terminal device 1has transmitted most recently is the random access preamble, the MACentity of the terminal device 1 monitors the random access response instep S403. When the received random access response includes acorresponding random access preamble ID (Yes in step S403), the MACentity of the terminal device considers (determines, deems) that thereception of the random access response has succeeded, and moves to thesubsequent procedure (not illustrated).

Note that, the terminal device 1 considers that the reception of therandom access response has failed when, after transmitting the randomaccess preamble, the terminal device 1 has not received the randomaccess response within the random access response window or the terminaldevice 1 has not received the random access response including therandom access preamble ID corresponding to the transmitted random accesspreamble (No in step S403).

Alternatively, in a case where the transmission data that the terminaldevice 1 has transmitted most recently is transmission data based on thescheduling information included in the random access response, the MACentity of the terminal device 1 performs a contention resolution in stepS403. In a case where the received downlink data includes the C-RNTI ofthe terminal device 1 or the transmitted Contention Resolution ID (Yesin step S403), the MAC entity of the terminal device considers(determines, deems) that the contention resolution has succeeded, andproceeds to the subsequent procedure (not illustrated).

Note that, when, after transmitting the transmission data based on thescheduling information included in the random access response, thecontention resolution has not succeeded before expiration of the timerrelating to the contention resolution (mac-ContentionResolutionTimer)(No in step S403), the terminal device 1 considers that the contentionresolution has failed.

When the reception of the random access response has failed or thecontention resolution has failed, the MAC entity of the terminal device1 increments a preamble transmission counter by one if power rampingsuspension has not been notified from the lower layer. The terminaldevice 1 confirms whether or not the value of the incremented preambletransmission counter (that is, the number of the preamble transmissions)has reached the maximum value (=preambleTransMax+1) (step S404).

When the number of the preamble transmissions reaches the maximum value(Yes in step S404), the MAC entity of the terminal device 1 transmitsthe indication (random access problem indication) indicating that arandom access problem occurs to the higher layer in step S405. At thistime, when the repetition level has not reached the maximum repetitionlevel value (the maximum value of the repetition level) supported by thecell, the terminal device 1 (MAC entity) may select the random accessresource in the next repetition level and execute the random accessprocedure. The maximum repetition level may be configured by the secondsystem information for each cell.

In other words, the terminal device 1 (RRC entity) receives theindication (information) indicating that the random access problemoccurs from the lower layer. At this time, the terminal device 1 (RRCentity) aborts the RRC procedure (RRC connection establishmentprocedure) which is being executed (step S406).

When the number of the preamble transmissions has not yet reached themaximum value (No in step S404), the MAC entity of the terminal device 1determines whether or not the UE timer (T308) has expired in step S407.When the UE timer has not yet expired (No in step S407), the terminaldevice 1 continues the random access procedure which is being executed.On the other hand, when the UE timer has not yet expired (Yes in stepS407), the terminal device 1 may abort the RRC procedure (in the presentexample, RRC connection establishment procedure) which is being executed(step S406).

Note that, when receiving, from the lower layer, the indicationindicating the occurrence of the random access problem on the normalcell while the first timer (T300) is in operation, the terminal device 1(RRC entity) may ignore the received indication and continue the RRCprocedure (that is, RRC connection establishment procedure). On theother hand, when receiving, from the tower layer, the indicationindicating the occurrence of the random access problem on the coverageenhanced cell while the second timer (T308) is in operation, theterminal device 1 (RRC entity) may abort the RRC procedure (in thepresent example, RRC connection establishment procedure) which is beingexecuted.

Furthermore, the terminal device 1 (RRC entity) counts the number oftimes of notification of the indication transmitted from the lowerlayer, and when the number of times of notification of the indicationhas reached a certain threshold value, the terminal device 1 may abortthe RRC procedure (RRC connection establishment procedure) which isbeing executed. The threshold value may be configured as a parameter ofthe random access configuration information included in the secondsystem information.

Alternatively, the MAC entity of the terminal device 1 may transmit anindication indicating the repetition level to the higher layer in stepS405. In other words, when receiving the indication (information)indicating the repetition level from the lower layer while the secondtimer (T308) is in operation, the terminal device 1 (RRC entity) mayabort the RRC procedure (RRC connection establishment procedure) whichis being executed.

Alternatively, the MAC entity of the terminal device 1 may transmit, tothe higher layer, an indication indicating that the repetition level hasreached the maximum repetition level supported by the cell in step S405.In other words, when receiving, from the lower layer, the indication(information) indicating that the repetition level has reached themaximum repetition level supported by the cell while the second timer(1308) is in operation, the terminal device 1 (RRC entity) may abort theRRC procedure (RRC connection establishment procedure) which is beingexecuted.

Furthermore, the terminal device 1 may initiate the RRC procedurewithout starting the timer (UE timer) relating to the RRC procedure. Inthis case, the terminal device 1 (RRC entity) may abort the RRCprocedure (RRC connection establishment procedure) which is beingexecuted on the basis of the indication transmitted from the lowerlayer.

Although the RRC connection establishment procedure has been mainlydescribed, the same method can also be applied to the RRC connectionre-establishment procedure which is executed, after the terminal device1 detects the radio link failure (RLF), to return from the Although, inthe RRC connection re-establishment procedure, the terminal device 1 isdifferent in that the T301 is used as the UE timer instead of the T300,the same method as in the RRC connection establishment procedure can beapplied to other many procedures such as a determination (configuration)method of the UE timer, and a starting method of the UE timer, forexample.

In such a constitution, when the terminal device 1 supports the CoverageEnhancement, the terminal device 1 can suitably configure the UE timerused for the RRC procedure executed by the terminal device 1 capable ofthe Coverage Enhancement, by using the information transmitted with thesystem information from the base station device 2 (cell) supporting theCoverage Enhancement. Furthermore, the base station device 2 cantransmit the UE timer relating to the RRC procedure used by the terminaldevice 1 supporting the Coverage Enhancement with the systeminformation.

Furthermore, the terminal device 1 can select and use one suitable UEtimer from among the multiple UE timers individually corresponding tothe repetition levels. Furthermore, the terminal device 1 can start theUE timer at suitable timing on the basis of the indication relating tothe random access procedure transmitted from the lower layer.Furthermore, the base station device 2 can provide the multiple UEtimers corresponding to the repetition levels with the systeminformation on the coverage enhanced cell.

This enables the base station device 2 and the terminal device 1 toexecute the RRC procedure using the suitable UE timer, and thus theefficient Radio Resource Control procedure can be realized.

Second Embodiment

A second embodiment of the present invention will be described below.

In the first embodiment, time (the number of repetitions) necessary forthe random access on the coverage enhanced cell is different dependingon the repetition levels, which requires that the timer (UE timer)relating to the RRC procedure be changed taking the repetition levelinto consideration. In the second embodiment, the UE timer configurationmethod based on a different random access procedure will be described.

For a handover procedure (RRC connection reconfiguration procedure)which is one of the RRC procedures, either the Contention based RandomAccess procedure or the Non-Contention based Random Access procedure isused. The handover procedure is an RRC procedure used for changing aprimary cell of the terminal device 1.

When causing (indicating) the terminal device 1 to perform the handover,the base station device 2 transmits an RRC connection reconfigurationmessage including Mobility Control Information (MobilityControlInfo).When the RRC connection reconfiguration message received from the basestation device 2 includes the mobility control information, the terminaldevice 1 initiates the handover procedure on the basis of theinformation of the message.

The mobility control information includes at least a physical cell ID ofthe cell (target cell) indicated as a handover destination, the commonradio resource configuration information on the target cell, the C-RNTI,and the UE timer (timer T304), and includes, as an option configuration,downlink frequency information and bandwidth information on the targetcell, and dedicated Random Access Channel configuration information(dedicated RACH configuration (RACH-ConfigDedicated)). The dedicatedRandom Access Channel configuration information may include a randomaccess preamble (preamble ID) information transmitted on the targetcell, transmission subframe information on the random access transmittedon the target cell.

Furthermore, the base station device 2 may include informationindicating whether or not the target cell is the coverage enhanced cellin the mobility control information. The base station device 2 mayinclude information on the UE timer (hereinafter, referred to as a timerT304bis) used for the handover procedure on the coverage enhanced cellin the mobility control information. Furthermore, the base stationdevice 2 may include the repetition level (or information indicating therepetition level) applied to the random access preamble on the targetcell in the mobility control information. The base station device 2 mayinclude the maximum value of the repetition level on the target cell inthe mobility control information.

The base station device 2 may not transmit the PDCCH or the EPDCCH forscheduling the random access response on the target cell. The terminaldevice 1 may directly monitor the random access response withoutmonitoring the PDCCH or the EPDCCH. The terminal device 1 may monitorthe random access response on the basis of a random access resource(preamble ID and transmission subframe) and the repetition levelindicated by the dedicated Random Access Channel configurationinformation.

Furthermore, the base station device 2 may include a random accessparameter corresponding to the number of repetitions necessary forperforming a random access resource selection on the target cell in thecommon radio resource configuration information. In other words, thebase station device 2 may include the multiple random access parameterscorresponding to the repetition levels in the common radio resourceconfiguration information. The multiple random access parametersinclude, for example, information relating to a random access preamblegroup, a subframe for transmitting the random access preamble, afrequency resource allocation of the uplink in which the random accessis performed, a frequency-hopping pattern, and the like.

An example of a LIE timer determination method of the terminal device 1in the handover procedure will be described with reference to FIG. 7.

The terminal device 1 in FIG. 7 receives the RRC connectionreconfiguration message including the mobility control information fromthe base station device 2. When information indicating the repetitionlevel is configured (notified, indicated) in the RRC connectionreconfiguration message (Yes in step S501), the terminal device 1 (RRCentity) starts the configured timer T304bis (second handover proceduretimer) as a timer (UE timer) relating to the handover procedure (stepS502).

Then, the terminal device 1 (RRC entity) reconfigures the radio resourceconfiguration of the terminal device 1 in accordance with aconfiguration (information element) included in the RRC connectionreconfiguration message, creates an RRC connection reconfigurationcomplete message, and provides (submits) the RRC connectionreconfiguration complete message to the lower layer.

Note that, the terminal device 1 (RRC entity) configures (notifies,indicates), for the lower layer, the repetition level informationnotified with the RRC connection reconfiguration message at this time.The lower layer (for example, MAC entity) for which the repetition levelis configured initiates the random access procedure for the target cell(step S503).

When the information indicating the repetition level is not configuredin the RRC connection reconfiguration message (No in step S501), therepetition level in the handover procedure needs to be determined(selected) in the terminal device 1.

At this time, the terminal device 1 (RRC entity) reconfigures the radioresource configuration of the terminal device 1 in accordance with theconfiguration (information element) included in the RRC connectionreconfiguration message without starting the VIE timer, creates the RRCconnection reconfiguration complete message, and provides (submits) theRRC connection reconfiguration complete message to the lower layer.

The random access procedure is initiated after the RRC connectionreconfiguration complete message is provided (submitted) from the RRCentity of the terminal device 1 to the lower layer of the terminaldevice 1. Therefore, after receiving the information (indication)relating to the repetition level from the lower layer, the terminaldevice 1 (RRC entity) needs to start the timer T304bis based on thereceived repetition level.

The lower layer (for example, MAC entity) initiates the random accessprocedure, when detecting that the transmission data is accumulated in abuffer in the higher layer (step S504). In other words, the RRC entityof the terminal device 1 provides (submits) the RRC connectionreconfiguration complete message to the lower layer, which in turncauses the MAC entity of the terminal device 1 to initiate the randomaccess procedure for transmitting the RRC connection reconfigurationcomplete message.

The terminal device 1 determines the repetition level during the randomaccess procedure (step S505). The repetition level in the terminaldevice 1 can be determined (selected) by using either (1) a repetitionlevel determined on the basis of the measurement result in the randomaccess resource selection or (2) a repetition level notified (allocated)from the base station device 2 during the random access procedure.

Note that, when the repetition level is notified (configured, indicated)from the base station device 2 during the random access procedure, therepetition level may be notified with the MAC control element, may beindicated by the random access response, or may be indicated by thedownlink control information notified on the PDCCH or the EPDCCH.Alternatively, the repetition level may be implicitly notified by thesubframe number and/or the frequency resource in which the random accessresponse is transmitted. The terminal device 1 maintains the currentrepetition level as it is, when the repetition level is not notified.

When the repetition level is determined during the random accessprocedure, the MAC entity of the terminal device 1 transmits theindication indicating the repetition level to the higher/upper layer(for example, RRC entity) of the terminal device 1 (step S506).

For example, when the terminal device 1 selects the (temporary)repetition level for transmitting the random access preamble, the MACentity of the terminal device 1 transmits the indication to the higherlayer of the terminal device 1. Furthermore, for example, when therepetition level is notified (indicated) from the base station device 2during the random access procedure, the MAC entity of the terminaldevice 1 transmits the indication to the higher layer of the terminaldevice 1. Here, the indication includes at least the repetition level ofthe terminal device 1 on the cell or information indicating therepetition level.

In other words, in step S506, the terminal device 1 (RRC entity)receives the indication including the repetition level information fromthe lower layer when initiating the random access procedure (whenperforming the random access resource selection) or during the randomaccess procedure.

The terminal device 1 (RRC entity) which has received the indicationdetermines the value of the timer T304bis as the timer (UE timer)relating to the handover procedure on the basis of the receivedrepetition level, and starts the operation of the timer T304bis (stepS507).

Note that, it is preferable that the value configured for the timerT304bis be configurable such that the maximum time thereof is longerthan the value configured for the timer 7304. For example, when as thetimer 7304 (first handover procedure timer), any value including 50 ms,100 ms, 150 ms, 200 ms, 500 ms, 1000 ms, and 2000 ms can be configured,it is preferable that, as the timer T304bis (second handover proceduretimer), any value including 500 ms, 1000 ms, 2000 ms, 3000 ms, 5000 ms,10000 ms, and 20000 ms be configurable. In this case, the same value maybe configured for the timer T304 and the timer T304bis.

Alternatively, the value configured for the timer T304bis may be a valuein a different range from that of the value configured for the timerT304, and furthermore may always exceed a value range configurable forthe timer T304. In other words, the same value cannot be configured forthe timer T304 and the timer T304bis. For example, as the timer T304(first handover procedure timer), any value including 50 ms, 100 ms, 150ms, 200 ms, 500 ms, 1000 ms, and 2000 ms can be configured, it ispreferable that, as the timer T304bis (second handover procedure timer),any value including 3000 ms, 4000 ms, 5000 ms, 10000 ms, 15000 ms, 20000ms, and 30000 ms be configurable.

When the base station device 2 makes notification of (configures) boththe timer T304 (referred to as the first handover procedure timer) andthe timer T304bis (referred to as the second handover procedure timer),the terminal device 1 may perform the handover procedure using the timerT304bis for the handover on the coverage enhanced cell (that is, thetarget cell is the coverage enhanced cell), or may perform the handoverprocedure using the timer T304 for the handover on the normal cell (thatis, the target cell is not the coverage enhanced cell).

Furthermore, when the base station device 2 makes notification of(configures) both the timer T304 and the timer T304bis, the terminaldevice 1 may use a timer value obtained by adding the value of the timerT304bis to the value of the timer T304 as the value of the T304.Furthermore, the terminal device 1 may use the timer T304bis as thetimer T304 when both the timer T304 and the timer T304bis are notified(configured).

In such a constitution, when the terminal device 1 supports the CoverageEnhancement, the terminal device 1 can appropriately configure the UEtimer, on the basis of the UE timer dedicatedly notified from the basestation device 2 or the indication relating to the random accessprocedure, in the handover procedure for the base station device 2(target cell) which supports the Coverage Enhancement and is a handoverdestination. Furthermore, when indicating the handover procedure for theterminal device 1 supporting the Coverage Enhancement, the base stationdevice 2 can dedicatedly transmit the UE timer used in the base stationdevice 2 (target cell) of the handover destination with the RRC message.

Furthermore, the terminal device 1 determines the repetition level byperforming the random access procedure on the target cell, which enablesthe terminal device 1 to select and use the suitable UE timer from amongthe multiple UE timers individually corresponding to the repetitionlevels. Furthermore, the terminal device 1 can start the UE timer at asuitable timing on the basis of the indication relating to the randomaccess procedure transmitted from the lower layer. Furthermore, the basestation device 2 can cause the terminal device 1 to select the suitableUE timer from among the multiple UE timers corresponding to therepetition levels, by dedicatedly notifying the terminal device 1 of theconfiguration of the target cell which is a coverage enhanced cell.

This enables the base station device 2 and the terminal device 1 toexecute the RRC procedure using the suitable UE timer, and thus theefficient Radio Resource Control procedure can be realized.

Note that, the above-described embodiments are merely examples, and canbe realized using various modification examples and replacementexamples. For example, the transmission scheme to be used can also beapplied to a communication system using the Frequency Division Duplex(FDD) scheme, the Time Division Duplex (TDD) scheme, or a combinationthereof in which each of the schemes is used for each frequency.Furthermore, the names relating to each parameter and various operationsindicated in the embodiments are used for the convenience ofexplanation. Even if the name actually applied and the name used in theembodiments of the present invention are different from each other, thegist of invention claimed in the embodiments of the present invention isnot affected.

For example, the number of repetitions relating to the transmissionand/or the reception for the Coverage Enhancement can be replaced with arepetition level, a Coverage Enhancement level, a coverage level, anenhancement coefficient (factor), an enhancement level, a repetitioncoefficient, an enhancement repetition coefficient, a bundling size, abundling coefficient, a trial frequency, a trial level, an attemptlevel, or a synonymous expression therewith.

Furthermore, “entity” used in each embodiment is a synonym for“sublayer.” In other words, description can be given in which the RRCentity, the PDCP entity, the RLC entity, and the MAC entity are replacedwith an RRC sublayer, a PDCP sublayer, an RLC sublayer, and a MACsublayer, respectively.

Furthermore, “connection” used in each embodiment is not intended to belimited to only a constitution in which one device and another deviceare directly connected using a physical line, but also is used for aconstitution in which the devices are logically connected with eachother and a constitution in which the devices are wirelessly connectedwith each other using radio technology.

Furthermore, specific numerical values used in the description aremerely examples of numerical value used for the convenience ofexplanation, and any suitable value may be used.

Furthermore, examples of the terminal device 1 include not only aportable-type or movable-type mobile station device, but also afixed-type or a stationary-type electronic apparatus installed indoorsor outdoors, for example, an audio-video (AV) apparatus, a kitchenapparatus, a cleaning or washing machine, an air-conditioning apparatus,office equipment, a vending machine, other household apparatuses ormeasurement apparatuses, an on-vehicle device, and devices, such as awearable apparatus, and a wearable health care apparatus, having acommunication function implemented therein. Furthermore, the terminaldevice 1 may be used not only for machine-to-machine communication(Machine Type Communication), but also for human-to-human communication,human-to-machine communication, vehicle-to-human communication,vehicle-to-vehicle communication, and on-road equipment-to-vehicle(road-to-vehicle) communication.

Furthermore, the terminal device 1 is also referred to as a userterminal, a mobile station device, a communication terminal, a mobilemachine, a terminal, User Equipment (UE), or a Mobile Station (MS). Thebase station device 2 is also referred to as a radio base stationdevice, a base station, a radio base station, a fixed station, a NodeB(NB), an evolved NodeB (eNB), a base transceiver station (BTS), or aBase Station (BS).

Note that, the base station device 2 is referred to as an NB in UMTS,and referred to as an eNB in EUTRA and Advanced EUTRA defined by the3GPP. Note that, the terminal device 1 in UMTS, EUTRA and Advanced EUTRAdefined by the 3GPP is referred to as UE.

Furthermore, although for the convenience of explanation, the method,the means, and the algorithm steps for realizing the functions or someof the functions of the units of the terminal device 1 and the basestation device 2 have been described with a specific combination thereofusing the functional block diagrams, these can be directly embodied byhardware, a software module executed by a processor, or combinationsthereof.

When implemented by hardware, the terminal device 1 and the base stationdevice 2 are each constituted of a power supply device or a batterysupplying power thereto, a display device such as a liquid crystaldisplay and a display driver, a memory, an input and output interfaceand input and output terminals, a speaker, and other peripheral devices,other than the constitution of the block diagram describe above.

When implemented by software, the functions of the terminal device 1 andthe base station device 2 can be held as one or more commands or codeson a computer-readable medium or can be transmitted. Thecomputer-readable medium includes both a communication medium and acomputer recording medium including a medium which helps carrying of acomputer program from one place to another place.

By recording one or more commands or codes on the computer-readablerecording medium, and causing the computer system to read and executethe one or more commands or codes recorded on the recording medium, theterminal device 1 and the base station device 2 may be controlled.Moreover, the “computer system” here refers to a computer systemincluding an OS and hardware components such as a peripheral device.

The operations described in each embodiment of the present invention maybe realized with a program. The programs run on the terminal device 1and the base station device 2 according to each embodiment of thepresent invention are each configured to control a CPU (program causinga computer to function) to realize the functions of the above-describedembodiments according to each embodiment of the present invention. Theinformation handled by these devices is temporarily held in a RAM at thetime of processing, and is then stored in various types of ROM or HDD,read out by the CPU as necessary, and edited and written.

In addition to realizing the functions of the above-describedembodiments by executing programs, the functions of each embodiment ofthe present invention may be realized by the programs runningcooperatively with an operating system, other application programs, orthe like in accordance with instructions included in those programs.

Furthermore, the “computer-readable recording medium” refers to aportable medium such as a semiconductor medium (for example, a RAM, anonvolatile memory card, or the like), an optical recording medium (forexample, a DVD, an MO, an MD, a CD, a BD, or the like), and a magneticrecording medium (for example, a magnetic tape, a flexible disk, or thelike), and a storage device such as a disk unit built into the computersystem. Moreover, the “computer-readable recording medium” includes amedium that dynamically retains the program for a short period of time,such as a communication line that is used to transmit the program over anetwork such as the Internet or over a communication circuit such as atelephone circuit, and a medium that retains, in that case, the programfor a fixed period of time, such as a volatile memory within thecomputer system which functions as a server or a client.

Furthermore, the above-described program may be configured to realizesome of the functions described above, and additionally may beconfigured to be capable of realizing the functions described above incombination with a program already recorded in the computer system.

Furthermore, each of the function blocks or features of the terminaldevice 1 and the base station device 2 used in each of theabove-described embodiments can be implemented or executed by ageneral-purpose processor, a digital signal processor (DSP), anapplication specific integrated circuit (ASIC), or any integratedcircuit (IC) for general-use, a field-programmable gate array signal(FPGA), or other programmable logical devices, a discrete gate or atransistor logic, a discrete hardware component, or a combinationthereof, which is designed to be able to perform at least the functionsdescribed in this specification.

Although the general-purpose processor may be a microprocessor, theprocessor may instead be a conventional processor, a controller, amicrocontroller, or a state machine. The general-purpose processor oreach circuit described above may be constituted of a digital circuit,may be constituted of an analog circuit, or may include both of them.

Alternatively, the processor may be implemented as a combination ofcomputing devices. For example, a DSP and a microprocessor, multiplemicroprocessors, one or more microprocessors connected to a DSP core, orother combinations of such constitutions may be used.

Although the embodiments of this invention have been described in detailon the basis of the specific examples, it is apparent that the gist ofeach embodiment of the present invention and the scope of claims are notlimited to these specific examples, design changes and the like withoutdeparting from the gist of this invention are also included. In otherwords, the description in this specification has been made for thepurpose of exemplary descriptions, and is not intended to impose anylimitation on each embodiment of the present invention.

Furthermore, various modifications are possible within the scope of thepresent invention defined by claims, and embodiments that are made bysuitably combining technical means disclosed according to the differentembodiments are also included in the technical scope of the presentinvention. Furthermore, a constitution in which the constituent elementsthat are described in each of the embodiments and exert the same effectare replaced with each other is also included in the technical scope ofthe present invention.

REFERENCE SIGNS LIST

-   1 Terminal device-   2 Base station device-   101, 201 Reception unit-   102, 202 Demodulation unit-   103, 203 Decoding unit-   104, 204 Reception data control unit-   105, 205 Physical layer control unit-   106, 206 Transmission data control unit-   107, 207 Coding unit-   108, 208 Modulation unit-   109, 209 Transmission unit-   110, 210 Radio resource control unit-   211 Network signal transmission and reception unit-   T01, T02 Transmit antenna-   R01, R02 Receive antenna

The invention claimed is:
 1. A terminal device communicating with a basestation device, the terminal device being configured to: when receiving,from the base station device, an RRC (Radio Resource Control) messageindicating a handover, the RRC message including information on a targetcell, random access information relating to a coverage enhancement levelof the target cell, and a timer relating to the handover, a maximumvalue among values of the timer relating to the handover in the terminaldevice that supports coverage enhancement exceeding a maximum valueamong values of a timer relating to a handover in another terminaldevice that does not support coverage enhancement, start the timerrelating to the handover; and execute a random access to the target cellusing the random access information relating to the coverage enhancementlevel of the target cell.
 2. The terminal device according to claim 1,configured to stop the timer relating to the handover when a problemoccurs in the random access to the target cell.
 3. The terminal deviceaccording to claim 1, configured to support, as a value of the timerrelating to the handover, a first timer value corresponding to a cell ofa coverage enhancement level requiring a repetition, and a second timervalue corresponding to a cell of a coverage enhancement level notrequiring a repetition.
 4. A base station device communicating with aterminal device, the base station device comprising: a processor: andmemory in electronic communication with the processor, whereininstructions stored in the memory are executable to: when causing theterminal device to execute a handover procedure using random accessinformation relating to a coverage enhancement level of a target cell,transmit, to the terminal device, an RRC (Radio Resource Control)message indicating a handover, the RRC message including information onthe target cell, the random access information relating to the coverageenhancement level of the target cell, and a timer relating to thehandover, a maximum value among values of the timer relating to thehandover in the terminal device that supports coverage enhancementexceeding a maximum value among values of a timer relating to a handoverin another terminal device that does not support coverage enhancement,the timer relating to the handover being started by the terminal device,and a random access to the target cell being executed by the terminaldevice using the random access information relating to the coverageenhancement level of the target cell.
 5. A communication method of aterminal device communicating with a base station device, thecommunication method comprising at least the steps of: when receiving,from the base station device, an RRC (Radio Resource Control) messageindicating a handover, the RRC message including information on a targetcell, random access information relating to a coverage enhancement levelof the target cell, and a timer relating to the handover, a maximumvalue among values of the timer relating to the handover in the terminaldevice that supports coverage enhancement exceeding a maximum valueamong values of a timer relating to a handover in another terminaldevice that does not support coverage enhancement, starting the timerrelating to the handover; and executing a random access to the targetcell using the random access information relating to the coverageenhancement level of the target cell.
 6. The communication methodaccording to claim 5, further comprising the step of stopping the timerrelating to the handover when a problem occurs in the random access tothe target cell.
 7. The communication method according to claim 5,wherein, the terminal device supports, as a value of the timer relatingto the handover, a first timer value corresponding to a cell of acoverage enhancement level requiring a repetition and a second timervalue corresponding to a cell of a coverage enhancement level notrequiring a repetition.
 8. A communication method of a base stationdevice communicating with a terminal device, the communication methodcomprising the step of: when causing the terminal device to execute ahandover procedure using random access information relating to acoverage enhancement level of a target cell, transmitting, to theterminal device, an RRC (Radio Resource Control) message indicating ahandover, the RRC message including information on the target cell, therandom access information relating to the coverage enhancement level ofthe target cell, and a timer relating to the handover, a maximum valueamong values of the timer relating to the handover in the terminaldevice that supports coverage enhancement exceeding a maximum valueamong values of a timer relating to a handover in another terminaldevice that does not support coverage enhancement, the timer relating tothe handover being started by the terminal device, and a random accessto the target cell being executed by the terminal device using therandom access information relating to the coverage enhancement level ofthe target cell.